Start running validate_solutions script for Travis CI (#3215)

* Removed print error_msgs at the end of test:

This was done only to reduce the message clutter produced by 60
failing tests. As that is fixed, we can produce the traceback in
short form and allow pytest to print the captured error message
output at the end of test.

* Start validate_solutions script for Travis CI

I am separating out the solution testing and doctest as validating
the solutions for the current number of solutions present is
taking 2 minutes to run.