Unit Tests / Code Coverage - Computational

[coatless]

Issue:

We have a very large code base with examples, but no "unit test" to test functionality (e.g. update function, do the values change, e.g. does it break?) outside of relying on CRAN example checks.

Furthermore, we have no real code coverage, which is a measurement that describes how much of the program's source code is tested by a particular test suite.

Solution:

1. Add more unit tests with testthat
2. Handle graphing requests with visualTest as suggested by http://stackoverflow.com/questions/30246789/how-to-test-graphical-output-of-functions