Add TOUCH support, deprecate finisher callable.

This commit adds instance methods to the Message class to carry out the finish,
requeue, and touch actions. These methods should be used in favor of the old
finisher callable, which will be removed in a future release.
bump version to 0.3.2
Merge pull request #4 from mreiferson/touch_4

TOUCH support
initialize last received timestamp on connect
Merge pull request #7 from mreiferson/ts_7

last received timestamp isn't initialized upon connection
better forwards/backwards compatibility options:

* fix TOUCH command
* deprecate async=True in favor of message instance methods
bump to 0.3.3-alpha / update documentation
Merge pull request #6 from mreiferson/docs_6

better forwards compatibility