Added --type-add and --type-set options from ack

These changes are centered around adding the `--type-add` and `--type-set` options from [ack](http://betterthangrep.com/).

In the [RelaxedGetoptLong branch](https://github.com/msabramo/rak/tree/RelaxedGetoptLong), I did one extra commit in order to support the use case of `--type-set new_type=.ext --new_type`. Because of the rigidity of `GetoptLong`, I had to do some acrobatics to make it work. I'm not super experienced with Ruby, so perhaps there is a better way.