implement getWebhookInfo method

Unit tests for Audio and User entity.
Thanks a lot @monster3d 

Add dependency for ext-mbstring, as suggested by @IronLady in #92

[skip ci]

Scrutinizer fixes

Close  #289

* upstream/develop:
  Added PHP version badge

* origin/master:
  Ask if a self-signed certificate is being used. [skip ci]
  Add issue and pull request templates.
  Update inline comments for hook.php and getUpdatesCLI.php Make sure that logging is set directly after Telegram object initialisation. (thanks @jacklul for pointing this out) Proofread and update utils.md file.
  Update readme and examples for enableAdmin(s) and add an extra test for string numbers.

Add new helper method entitiesArrayToJson.