Dramatically sped up tests

By stubbing the pronunciations instead of processing the entire file the tests dropped from 2.3s to 0.1s. Half of the new time is from `data_reader_spec.rb:8` which still reads the pronunciations file, just doesn't process it.

I didn't stub loading the phones or symbols because in the case of the phones the time savings was trivial and the stubbing would have been rather pervasive and in the case of the symbols creating the stub actually took more time than reading the file.