Moving towards a slightly more standard project layout

Putting 'require_relative' in every file is going to get old fast and will cause problems when we start moving files around. The more standard approach is to place source files in the `lib/` directory and then to arrange them into subdirectories around modules. 

The `require` statements are now in `lib/ROQTI.rb` and the executable test file is in `test/`. When adding a new file, a single `require` statement can be placed in `lib/ROQTI.rb` rather than worrying about which files will need it.