Updated travis.yml file to use pip + the requirements/test.txt file
Reverted to older unittest.TestCase.assertRaises form.
This form is compatible with Python 2.6.

Fixes the failures found with Travis builds [53, 54]
Remove "--use-mirrors" argument to pip install (deprecated)
Applied PEP8 and Pyflakes style guidelines to fastkml source code using the
following style checkers:
* pep8 (version 1.5.7)
* pyflakes (version 0.7.3)