fix(eslint): Add no-implicit-coercion rule

.eslintrc.js

         'no-extra-label': 2,
         'no-fallthrough': 2,
         'no-floating-decimal': 2,
+        'no-implicit-coercion': 2,
         'no-implicit-globals': 2,
         'no-implied-eval': 2,
         'no-iterator': 2,

JitsiConference.js

  * Check if user is logged in.
  */
 JitsiConference.prototype.isLoggedIn = function() {
-    return !!this.authIdentity;
+    return Boolean(this.authIdentity);
 };
 
 /**

modules/RTC/RTCBrowserType.js

         // This mirrors what sdp-simulcast uses (which is used when deciding
         // whether to actually enable simulcast or not).
         // TODO: the logic should be in one single place.
-        return !!window.chrome;
+        return window.chrome !== undefined;
     }
 
     // Add version getters for other browsers when needed

modules/RTC/RTCUtils.js

  * @param stream the stream we received from calling getUserMedia.
  */
 function setAvailableDevices(um, stream) {
-    const audioTracksReceived = stream && !!stream.getAudioTracks().length;
-    const videoTracksReceived = stream && !!stream.getVideoTracks().length;
+    const audioTracksReceived = stream && stream.getAudioTracks().length > 0;
+    const videoTracksReceived = stream && stream.getVideoTracks().length > 0;
 
     if (um.indexOf('video') != -1) {
         devices.video = videoTracksReceived;
                                     && !containerSel.is(':visible')) {
                                 containerSel.show();
                             }
-                            const video = !!stream.getVideoTracks().length;
+                            const video = stream.getVideoTracks().length > 0;
                             if (video && !$(element).is(':visible')) {
                                 throw new Error(
                                     'video element must be visible to attach'
                     this.getUserMediaWithConstraints(
                         options.devices,
                         function(stream) {
-                            const audioDeviceRequested = options.devices.indexOf('audio') !== -1;
-                            const videoDeviceRequested = options.devices.indexOf('video') !== -1;
-                            const audioTracksReceived = !!stream.getAudioTracks().length;
-                            const videoTracksReceived = !!stream.getVideoTracks().length;
+                            const audioDeviceRequested
+                                = options.devices.indexOf('audio') !== -1;
+                            const videoDeviceRequested
+                                = options.devices.indexOf('video') !== -1;
+                            const audioTracksReceived
+                                = stream.getAudioTracks().length > 0;
+                            const videoTracksReceived
+                                = stream.getVideoTracks().length > 0;
 
                             if((audioDeviceRequested && !audioTracksReceived)
                                 || (videoDeviceRequested && !videoTracksReceived)) {
         if (!rtcReady) {
             throw new Error('WebRTC not ready yet');
         }
-        return !!(
-            navigator.mediaDevices
-                && navigator.mediaDevices.enumerateDevices
-                && typeof MediaStreamTrack !== 'undefined'
-                && MediaStreamTrack.getSources);
+        return Boolean(navigator.mediaDevices
+            && navigator.mediaDevices.enumerateDevices
+            && typeof MediaStreamTrack !== 'undefined'
+            && MediaStreamTrack.getSources);
     }
 
     /**

modules/RTC/ScreenObtainer.js

      * @returns {boolean}
      */
     isSupported() {
-        return !!this.obtainStream;
+        return this.obtainStream !== null;
     },
 
     /**

modules/xmpp/JingleSessionPC.js

          */
         this.ssrcOwners = {};
 
-        this.webrtcIceUdpDisable = !!options.webrtcIceUdpDisable;
-        this.webrtcIceTcpDisable = !!options.webrtcIceTcpDisable;
+        this.webrtcIceUdpDisable = Boolean(options.webrtcIceUdpDisable);
+        this.webrtcIceTcpDisable = Boolean(options.webrtcIceTcpDisable);
         /**
          * Flag used to enforce ICE failure through the URL parameter for
          * the automatic testing purpose.
          * @type {boolean}
          */
-        this.failICE = !!options.failICE;
+        this.failICE = Boolean(options.failICE);
 
         this.modificationQueue
             = async.queue(this._processQueueTasks.bind(this), 1);

modules/xmpp/SdpTransformUtil.js

         this.mLine.ssrcGroups = ssrcGroups;
     }
 
-    /**
-     * Checks whether the underlying media description contains given SSRC
-     * number.
-     * @param {string} ssrcNumber
-     * @return {boolean} <tt>true</tt> if given SSRC has been found or
-     * <tt>false</tt> otherwise.
-     */
-    containsSSRC(ssrcNumber) {
-        return !!this._ssrcs.find(
-            ssrcObj => ssrcObj.id == ssrcNumber);
-    }
-
     /**
      * Obtains value from SSRC attribute.
      * @param {number} ssrcNumber the SSRC number for which attribute is to be
      * <tt>false</tt> otherwise.
      */
     containsAnySSRCGroups() {
-        return !!this.mLine.ssrcGroups;
+        return this.mLine.ssrcGroups !== undefined;
     }
 
     /**
     addSSRCGroup(group) {
         this.ssrcGroups.push(group);
     }
-}
+}

modules/xmpp/moderator.js

     elem.c(
         'property', {
             name: 'disableRtx',
-            value: !!this.options.conference.disableRtx
+            value: Boolean(this.options.conference.disableRtx)
         }).up();
     elem.c(
         'property', {