Modified Rake Object

[calixo888]

There are a lot of getters inside of the Rake object that don't need to be there. They only exist to return the already-accessible fields of the Rake object. I got rid of all of the getter methods and changed the names of some of the Rake fields. I also modified the input parameters of the Rake object to take in the target text to analyze, and added a setter method to change the text of the Rake object and update all corresponding fields.

Also, there are a lot of public fields that shouldn't be public, it gives the initialized a bad look. So I modified multiple fields to private, including metric, to_ignore, min_length, and max_length. I also figured some users may want to modify the stopwords or the punctuation to change the outcome metrics of the Rake object, so I created setters for both the stopwords and punctuation, and had the metrics of the Rake object be refreshed after the stopwords/punctuation changed.

I would greatly appreciate it if you made me a contributor, because I am very much interested in contributing more to this project, I think it's very interesting.