Added support for python3, while maintaining compatibility with python2
Merge pull request #12 from mbologna/develop

Added support for python3, while maintaining compatibility with python2
Try file 'PKG-INFO' or 'METADATA' to retrieve package metadata

Some packages seem to store the metadata in a file called 'METADATA' instead
of 'PKG-INFO'. Probably the change is related to a newer pip or setuptools
version but I don't know for sure.
Merge remote-tracking branch 'eht16/develop'

Conflicts:
	yolk/metadata.py
Get metadata correctly
Preserve metadata order