Add unit tests to / prune dead code from driver

[gavanderhoorn]

As commented by @gonzalocasas in #8 (comment), there are programs (VAL 3 terminology) in the library and application that are not used right now.

As a large part of the VAL 3 code implements (parts) of a simple_message library, it would be good to create a set of unit tests that exercises relevant execution paths so as to gain (and keep) trust in that code.

Having a set of tests would also allow us to prune the code in places that appear to not be used and also don't pass certain levels of testing.

Using the tests as regression tests would reduce the chance of introducing regressions as well.

[gavanderhoorn]

@marshallpowell97: I'm not aware of any official testing infrastructure in VAL 3 and/or the SRS, but in a test would simply be a program that exercises a certain part of the functionality offered by ros_libs or ros_server.

We could use simple print outs (ie: plain text output by the programs) to verify they succeed.

[gavanderhoorn]

#10 also connects to this.