All request parameter are optional

In this issue the tdlib team explicitly states, that all request parameters can be null. This is now represented in the swift version, but making all parameters optional.

Fix Logout Crash

Thanks to @nikit6000 the crash after logout should be fixed.

Sync with tdlib v1.6.0

Uses new version of tdlib.

Sync with tdlib v1.5.0

Update to tdlib v1.5.0

Make open source

0.1.6

update gems

Merge remote-tracking branch 'origin/master' into develop

0.1.5

Merge remote-tracking branch 'origin/master' into develop