Add automated testing via Travis CI.
Override default install (no requirements.txt).
Use .format syntax compatible with Python 2.6.
Clean up imports.
Stop using 'with', which is illegal in Python < 2.5.
Add trailing new line.
Stop testing Python 3.2 (not supported).
Stop testing Python 2.4 (not supported by Travis).
Add simplejson requirements.txt for testing (required by Python 2.5).
Add testing requirements to PyPI.
Remove occurences of str.format for Python 2.5 compatibility.
Fix whitespace.