Flask support for json and unknown content type posted data.

Relevant to #41
Fix test body content flask test.
Pep cleanups. Lots of unused modules removed.
Fixed the flask python 3.4 compatibility.
Enabled python 3.4 on travis.
Updated flask body content test.
Merge branch 'includes_posted_data' of https://github.com/stas/bugsnag-python into stas-includes_posted_data

Conflicts:
	.travis.yml
Merge branch 'stas-includes_posted_data'