cleaned up and similar styles for testing

This switches out the infix overloading from Bob, which
was cool but possibly confusing. Now a function named
`equal` is used in both the Python and R files, to similar
effect. Would be good to test this more, but I think it
should be good to go.
Merge pull request #96 from ajschumacher/approximate_tests

cleaned up and similar styles for testing - resolves #90