Add support for Pry when exceptions occur

[hopsoft]

When a test fails due to an unhandled error, I would prefer that MicroTest take you directly to the failing code rather than exiting the test run. At least if the --pry option was used for the run.

Look into using https://github.com/conradirwin/pry-rescue or https://github.com/pry/pry-exception_explorer for this.

[hopsoft]

Done