Add tests

[giordano]

Travis is setup for this repository but it currently only checks that the program can be built without errors. There is a file in the test/ directory with a single assertion, but this doesn't seem to be used anywhere for automatic testing.

Tools that could be used to perform the tests are

• Catch2
• Boost.Test

The second one has the advantage to be already a dependency of the program and it's already used in the file in test/ directory.

[EiffL]

I would rather argue for Boost.Test

The existing file in test/ was just a prototype, never actually implemented tests :-(