More robust testing when kpsewhich isn't present
 fix pathname lookup logic to always precede kpsewhich with pathname_find
 meaningful comment on the TeX pathanme_find lookup
 skipped tests always announce themselves. latexmlc invocation is now a little more portable
 adding requirements for all TeX-dependent tests
Merge pull request #24 from dginev/skip_tests_on_missing_TeX

 More robust testing without a TeX installation