A few random fixes

[paulromano]

This pull request closes #17 and #18 and fixes a few other things:

• Implement a better way of showing default arguments for test.py
• Raise IOError instead of calling exit()
• Updates a few docstrings and adds (object) to class definitions

[paulromano]

Note that I changed the extension on the README from md to rst (since the file was formatted as restructuredText, not markdown).

[cjosey]

Other than the comment I made on the IOError, I see no issues.

[paulromano]

Ok, I reverted to calling print, but changed the exit() to raise so that the original exception/traceback are shown.

[cjosey]

It all looks good. Thanks for the fix!