Cleanup: Remove a useless try/except.

Encoding a unicode string to utf8 cannot fail, so we don't want any
exception occuring there to be missed.
Use ordereddict from pypi for python < 2.7
Let nose run coverage
Import directly from six when possible instead of compat.py so we can clean it a little
Append TestResponse.normal_body method documentation
Append some documentation about webtest.debugapp
Fix bug in debugapp.txt documentation code source example
Merge https://github.com/cdevienne/webtest
Merge https://github.com/harobed/webtest
Tests some cases with no content type header or a response having body whereas it should not
Refactor status check (and improve coverage of this function)