Improvements for openjournals/joss-reviews#2044

[majensen]

For https://github.com/openjournals/joss-reviews/issues/2044

• Generated cruft files are removed from the repo.
• README now clarifies what OpenMP is and points to more info for the user.
• Makefile can perform a check of OpenMP compliance : run make check
• test/test.sh performs a rational comparison of baseline run and test run
  • See this comment for details: https://github.com/majensen/neep/commit/787b474b650eaaeb9d62928880054f12d4f7d63c#commitcomment-40530849
  • Also, see this comment https://github.com/majensen/neep/commit/cba34e08f415cc71dde379c1bc453711d6f75ee6#commitcomment-40531018 that refutes a suggestion in the original README.md

[scwest]

Whoa, Mark. You have gone out of your way and made some substantial quality of life improvements, here. Thank you.