Added better log handler support with severity
Ignore stacktrace lines from logging module
Added logging import
Send partial LogRecord event in extra ata
Added documentation for LOGGING support
Fixed docs styling
Create exception class name using record level (easier to see)
Small clean up improvement
Don't call iter() on app

WSGI middlewares are required to be iterables, not iterators. This means
that their __iter__() method may not return self, and so the .close()
method will not be preserved.
Try to be more resiliant in the face of failure [Closes #31]

Python 2.x sets all global variables to None during shutdown (including
imported modules).

This means that Bugsnag could quite reasonably crash at any time,
regardless of how carefully we write the code.

So, add some more exception handlers...

There's probably no way to catch absolutely everything, so let's see
how well this does in the wild.
Minor fixes

1. don't rely on load order to ensure bugsnag config is loaded before
logger
2. don't crash if some fields are missing from log records
3. Use .getMessage() instead of .message
Merge branch 'foxx/master'
Fix super call on python2.6