Adding SameAs and NotSameAs operators

Signed-off-by: Christophe Sicard <sicard.christophe@gmail.com>
Adding tests and docs to SameAs and NotSameAs operators
Merge pull request #14 from tophsic/sameasnotsameas

Adding SameAs and NotSameAs operators
Merge branch 'master' of https://github.com/bobthecow/Ruler