C++ tests

[mikemorris]

The Node.js tests should move out with the Node.js bindings. Need to add some unit tests (using Catch, Boost.Test or something else?) to actually test the core C++ library.

[springmeyer]

Since the code currently depends on boost, using boost for tests would be reasonable and adds no dependencies. When testing with boost I prefer boost/detail/lightweight_test.hpp which is header-only and not Boost.test which requires the libboost_test library to be built.

However Catch is great and would be the best choice for libs that don't already depend on boost.

[springmeyer]

we now have 100% test coverage via javascript mocha tests in #80