Changed String types to ByteString and added new directories for source files.

I also updated the readme. Note that the image in the readme that shows the build status links to [MarcoSero/Norvigs-Spelling-Corrector](https://github.comMarcoSero/Norvigs-Spelling-Corrector), not my fork, so you should enable Travis CI for your repo to make it work.

Feel free to reject / require things. I just did this for fun.