Cherry pick b53a461ea6cba6d906a1dc012aee96ef1ab7dcbd from basicruby
Cherry pick b18b4810e13444ac5e5c4c0121da8140554aa3bf from basicruby: Better error message when I forget to put 'bundle exec' before rspec.
Cherry pick 35b3c83b22b8ea4b7386a878d360a4409a9bfa8f from basicruby: Comments to explain why I redefine puts and gets for Opal.
Cherry pick 1a3307fd1260b9a396af4df013c32b72915c755e from basicruby: Bug fix: special variable __method_name was incorrectly part of the closure's @env, so it overwrote the closure's real __method_name.
Cherry picking 39cf69f395dc75b8d4fea0fbe2a2000085ca2afc from basicruby: Now also testing curriculum that calls "gets" -- lots of bugs found.
Change requires to require_relative.