Proposal: make UnirestException a RuntimeException

[joshgontijo]

From #181

Hello,
A few months ago I started using UniRest and I have mostly enjoyed it. The one criticism is that UnirestException is checked. I would like to propose that it be changed to a RuntimeException for the following reasons:

Checked exceptions do not work well (or at all) with Java 8 streams and poorly with lambdas in general without writing your own checkable function library. This makes using Unirest in a stream or lambda painful
UnirestException is generic in of itself and provides no clue about what you want the developer to do in case it happens without unpacking the exception to look at the "real reason". As such it's no better than a RuntimeException and is far more annoying.
Checked Exceptions have mostly been abandoned as a failure by pretty much every post-java language in existence. https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=checked%20exceptions%20are%20evil