New labelCompare Function

• Fix for #11 - thanks @furlongm
• Addition of labelCompare function to serve as a drop-in replacement for the same function in the rpm package, again thanks to @furlongm
• Converted tests to py.test format
• Improved logging efficiency

0.2.3 Release

The only functional change in this release is a bugfix for issue #7, where a package string with no epoch and a multi-digit primary version, e.g. firefox-45.0-4.fc22.x86_64, would be parsed incorrectly such that the epoch was 4 and the version was 5.0.

Thanks to @thoger who pointed out the bug and proposed the implemented fix.