Fix find call for ruby 2.1.1

Find in 2.1.1 expects a string, I guess? This commit changes match_tree to give a
string to Find.find instead of a Pathname (which works fine in every earlier
version of ruby but not this one)
helpful error when simplecov fails

this commit adds an explanation for why simplecov might have failed that prints
to stderr.
add script to test multiple ruby versions

because I don't run things if they aren't right there
ignore more files

remove junk that doesn't belong in gems
remove gemfile.lock

not necessary for gem library