Merge fix on Avatar into develop

Avoid Realm queries for messages with null users

Fix on building the default avatar

Fix crash when building default avatar 

Handle odd usernames with dots such as ..., .Foo., .., Foo.. which as causing a crash when building the default avatar image

Merge branch 'fix/filtering_get_messages_flood' of github.com:RocketChat/Rocket.Chat.Android into fix/filtering_get_messages_flood

Handle odd usernames with dots such as ..., .Foo., .., Foo.. which as causing a crash when building the default avatar image

Initial Crashlytics support

Merge branch 'fix/filtering_get_messages_flood' of github.com:RocketChat/Rocket.Chat.Android into fix/filtering_get_messages_flood

this using the newly added ping call without the use of bolts'
callbacks.
Implemented a TaskService class that is used to do the work offloaded
by the GcmNetworkManager which is used here to schedule
keep-alive recurring tasks.

Close the socket if we get an error because MethodCallHelper class keep a reference to socket and it has objects spread all over the place. Thus this may cause inconsistencies that are hard to keep track, so it's safer to close the socket so that the websocket thread will know and try to reconnect.

this using the newly added ping call without the use of bolts'
callbacks.
Implemented a TaskService class that is used to do the work offloaded
by the GcmNetworkManager which is used here to schedule
keep-alive recurring tasks.

Close the socket if we get an error because MethodCallHelper classe keep a reference to socket and it has objects spread all over the place. Thus this may cause inconsistencies that are hard to map, so it's safer to close the socket so that the websocket thread will know and try to reconnect.

Needed to add provided dependencies since AS Canary 9 and AS beta 1 seem not to find them from the other project dependencies

Closes #379

Wrapped nullable String returned to onNext with an Optional to avoid NPE eventually happening since RxJava 2.x does not support it

Do not truncate tables on initialize for those subscribers. By doing that way, the RealmUser tables were being deleted from Realm which was causing the message-user relationships to sink