Ready for 0.3.0 release.
Check for sys.maxunicode when generating utf8

This avoid generating a invalid unicode character in a narrow Python
build
Merge pull request #29 from elyezer/fix-unicode-range

Check for sys.maxunicode when generating utf8
Prepare for 0.3.1 release.
Added Python shield to README file.

See https://pypip.in/python_versions.html
Added License badge to README.rst