Replacematcherror - catch exceptions and convert to internal error. (#424)

* Catch exceptions and convert to internal error.
We need to update the displayed message to incorporate a line number and text to be used for the issue.

* Cleanup exception handling/throwing.
Re-throw expected (or uncorrectable exceptions).
Provide Utils.getThrowable() to get the first (eldest) or last throwable in the chain.
Update tests to conform to FreeSpec protocol.

* Minor cleanup
Admit we've updated some deprecated ScalaTest methods.