For the most part the changes are taking the "static propTypes" declaration off
of components and declaring them as Flow types. Sometimes to support flow some
method signatures had to be added. There are some exceptions in which more had
to be done to tame the beast:
- AbstractVideoTrack: put in additional truthy checks for videoTrack.
- Video: add truthy checks for the _videoElement ref.
- shouldRenderVideoTrack function: Some component could pass null for the
  videoTrack argument and Flow wanted that called out explicitly.
- DisplayName: Add a truthy check for the input ref before acting on it.
- NumbersList: Move array checks inline for Flow to comprehend array methods
  could be called. Add type checks in the Object.entries loop as the value is
  assumed to be a mixed type by Flow.
- AbstractToolbarButton: add additional truthy check for passed in type.

* fix(connection): reload immediately on possible split-brain

There isn't an explicit way to know when a split brain
scenario has happened. It is assumed it arises when an
"item-not-found" connection error is encountered early
on in the conference. So, store when a connection has
happened so it be calculated how much time has
elapsed and if the threshold has not been exceeded
then do an immediate reload of the app instead of
showing the overlay with a reload timer.

* squash: rename isItemNotFoundError -> isShardChangedError

ESLint 4.8.0 discovers a lot of error related to formatting. While I
tried to fix as many of them as possible, a portion of them actually go
against our coding style. In such a case, I've disabled the indent rule
which effectively leaves it as it was before ESLint 4.8.0.

Additionally, remove jshint because it's becoming a nuisance with its
lack of understanding of ES2015+.

Prepare for React 16.

The functions need not return anything, or it will be dispatched as another
action.