Added the create, destroy, list and list IDs mute(s) endpoints.

Roughly modelled on the similar-ish block user functions (note: the
"mutes/users" instead of just "mutes" appears to be intentional by
Twitter).

Also added myself to AUTHORS.rst because I reckon adding API bits makes
the grade.  ;)
Added muting to test suite.

I should have checked for this earlier, ah well, 'tis here now.
Again, basically a copy of the blocking code updated for muting.

Excellent target to test it on too.
Fixed typo with list_mute_ids.
Merge pull request #352 from Hasimir/mutes

Mute endpoints for the API