Change data structure to queue and overload the Use method to take http....

...Handler and negroni.Handler

I made a fairly big change as it started out as a fork to make a personal project rather than a contribution. But I figured since I learned a lot from this project, I thought it would be nice to share my take. Also, I'm not 100% confident about integration tests with other modules like NewResponseWriter, but it passed the current tests with flying colors. 


A couple of things to note:

<code>Use()</code> will now take either http.Handler or negroni.Handler objects.
<code>Use()</code>'s performance is now <code>O(1)</code> compared to the previous <code>O(N)</code>
There's also no more overhead keeping an array as well as a linked list.