timout for `sendMessage`

[bluemix]

Telegram is down for a while today, which caused some messages to be halt.
It would be better if there is a parameters, e.g., timeout (milliseconds), that can be set when
sending a message:

Example:

teledart.telegram.sendMessage(myTelegramChatId, 'Hello', timoeut: 1600)

Thanks in advance.

Hey @bluemix, did you work on this feature?

[bluemix]

@eherediadev ah, no I didn't

@DinoLeung are you working on this feature?

@eherediadev ah, no I didn't

If no one is working with this, I'll start working on it.

[DinoLeung]

Timeout should be set in telegram.dart and apply to all API calls except getUpdates. Will work on this in the near future