Fixes #734
NOTE: Currently not testing StickerSet in terms of bot methods (interaction with telegrams servers) as there's no delete operations.
- Added all the new and shiny features from API 3.1. - Not API 3.1 changes: - Use future.utils.string_types for string isinstance checks. - Stall between retries of test_set_webhook_get_webhook_info() & test_delete_webhook().
refs #650