Upgraded Test Suite for Compiler Options, MPI, HDF5, PETSc

This pull request allows developers to run the test suite for all different compiler options that are featured in test_compile. This can be performed with a simple python script called ```run_tests.py```.  Because data cannot be sent directly to nosetests, a nosetest plugin was created to communicate information about parallelization when running with MPI=yes configurations of OpenMC. 

In order to use this option now, this plugin must first be installed by navigating to the tests sub-directory and typing ```sudo python setup.py install```.

This test suite can now be checked running in parallel and generating HDF5 statepoint/particle restart/summary files. Also CMFD tests have been added such that PETSc can be tested. 

The precision of results have been changed from 14.8f to 12.6E. All results were checked to make sure this conversion was successful.