To make all bots consistent add shared function in bot_lib.py
to check if this bot is called. All bots respond to at-mention of
the bot instead of their specific names.
Now all the bots that are stored in contrib_bots are in the
same file/directory format.
The format is specified here #3427. Add tests.py file for encrypt_bot as well.
Fixes#3427.
In order to make the layout of all bots consistent, this commit
moves each bot into a folder with its name and modifies 'run.py'
so that only bots with such a structure can be executed. 'lib'
gets renamed to 'bots'.
