Don't call logging.basicConfig if logging is already configured (#775).
Will not call logging.basicConfig if there is a root logger,
tornado logger or tornado.application logger.

Updated patch to reflect comments about tests and method privacy.
Correct example variable, use consistant quoting
Merge pull request #971 from gmr/logging-patch

Don't call logging.basicConfig if logging is already configured (#775). Replaces #887
Merge commit 'c2a25a'

* commit 'c2a25a':
  Correct example variable, use consistant quoting

Closes #972
Remove inaccurate IOLoop logging test cases.
Move _setup_logging to BaseIOLoop and use it in asyncio and twisted implementations.
Improved extensibility of LogFormatter

* refactored code separating coloring logic
* allow full line customization of the format
* possibly faster operation
Rename "normal" to "end_color" in log format strings.

When not colorizing, use empty strings instead of two copies of "normal".

Update docs.
Add trollius (py2 backport of asyncio) to tox config.

This passes the twisted integration tests but currently has some issues
with pycurl.