Merge pull request #25 from robdennis/master

now always using catch_warnings to test deprecation message
Merge pull request #27 from robdennis/master

#14 - moved over exception tests to py.test
Merge pull request #28 from robdennis/master

fixes #26 - added check for python versions < 2.6 with error message
Merge pull request #29 from robdennis/master

#14 - finished refactored a half-done doctest to py.test