Integrate OneGraph's GraphiQL Explorer. <br/>
@sgrove in #199
Make sure devtools can be used when the transport layer is websockets
only. <br/>
@kamerontanseli in #163
Debounce broadcast messages to improve devtools responsiveness and
memory usage. <br/>
@thomassuckow in #173
Gracefully handle a failed version compatibility check. <br/>
@mjlyons in #201
Increase timeout when checking whether to display the devtools panel. <br/>
@Gongreg in #203
Fully reload devtools when a page reload happens, to make sure it is
reconnected to the current Apollo Client instance properly. <br/>
@hwillson in #205