added ruby 2.1.3 in the ci rubies to test the project on
fixed ca_file integration test
fixed the last integration test

thanks to @pcorliss
on
https://github.com/rest-client/rest-client/commit/d242580dd57d5abe34e890
c6efe1e88c1a96bbc4 commit, because I couldn’t figure it out how to
provide the certificate files to make the tests pass
Merge pull request #5 from formigarafa/fix_failing_tests

Fix failing tests