Adding satisfies function and tests

Signed-off-by: Zachary King <zchrykng@gmail.com>
Adding tests

Signed-off-by: Zachary King <zchrykng@gmail.com>
Making tests match unittest discover pattern

Signed-off-by: Zachary King <zchrykng@gmail.com>
Merge branch 'master' of https://github.com/zchrykng/python-semver

Conflicts:
	semver.py