Add methods for exposing internal state

[jwerle]

Hi @blakeembrey,

I hope you are doing well. This pull request introduces 4 methods on the pluralize function that expose the internal state of this module. The intended purpose of this methods could be for introspection on how this module may handle a word given to it. Consider the word audio as an example. The plural form of this word is also audio. However, there are accepted uses of the alternative plural form of this word: audios. While this may not be heard or spoken often for English speakers, it could become common in computer speak, like resource naming in APIs. I hope this makes sense

[coveralls]

Coverage remained the same at 100.0% when pulling fe262ec3f1d1072ed2a189809974022124cff42a on jwerle:master into e507706be779612c06ebfd6043163e063e791d79 on blakeembrey:master.