fix(telegram): make channel/group mentions work

[wass3r]

❤ THANKS FOR HELPING OUT :D

Proposed change

Add better support for calling upon bot from groups and channels. Also, adds support for using slash commands, ie. you can either do @botname help or /help. i'm not heavy telegram user - let me know if slash commands are supposed to be used differently.

Types of changes

What types of changes is this pull request introducing to flottbot? Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

You can fill this out after creating your PR. Put an x in the boxes that apply

• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[coveralls]

Pull Request Test Coverage Report for Build e00e3d9083d1a1f2bd043a273ea071f3c4d5acce-PR-147

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 45 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.9%) to 36.674%

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Files with Coverage Reduction	New Missed Lines	%
remote/telegram/remote.go	45	0%

Totals
Change from base Build 65ce0f30a0ae7d545576b5488a75ea76d64f2dfa:	-0.9%
Covered Lines:	838
Relevant Lines:	2285

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💛 - Coveralls