deps: update to Babel 7

package.json

     "yaeti": "1.0.1"
   },
   "devDependencies": {
-    "babel-core": "6.26.0",
-    "babel-eslint": "8.0.3",
-    "babel-loader": "7.1.2",
-    "babel-preset-env": "1.6.1",
-    "babel-preset-flow": "6.23.0",
-    "babel-preset-stage-1": "6.24.1",
+    "@babel/core": "7.1.2",
+    "@babel/plugin-proposal-class-properties": "7.1.0",
+    "@babel/plugin-proposal-export-namespace-from": "7.0.0",
+    "@babel/plugin-transform-flow-strip-types": "7.0.0",
+    "@babel/preset-env": "7.1.0",
+    "@babel/preset-flow": "7.0.0",
+    "babel-eslint": "10.0.1",
+    "babel-loader": "8.0.4",
     "core-js": "2.5.1",
     "eslint": "4.12.1",
     "eslint-config-jitsi": "github:jitsi/eslint-config-jitsi#v0.1",

webpack.config.js

             options: {
                 presets: [
                     [
-                        'env',
+                        '@babel/preset-env',
 
                         // Tell babel to avoid compiling imports into CommonJS
                         // so that webpack may do tree shaking.
                         { modules: false }
                     ],
-                    'flow',
-                    'stage-1'
+                    '@babel/preset-flow'
+                ],
+                plugins: [
+                    '@babel/plugin-transform-flow-strip-types',
+                    '@babel/plugin-proposal-class-properties',
+                    '@babel/plugin-proposal-export-namespace-from'
                 ]
             },
             test: /\.js$/