Put the "Transactions" module behind an option setting

Hi @vandre, I'm a big fan of this. I wanted to allow the transactions module to sit behind an option like the other modules.  

I tried to do quite a bit of testing, but I recommend doing a pass on your own before pushing to the store in case I missed something. 

Notes:
- I separated out the transactions module code into it's own file. 
- I removed some of the extra code copied from a stack overflow answer that wasn't needed.
- ~~I changed $.get into a global httpGet method. While jquery wasn't used in this extension, I made the mistake of assuming [jquery.get](http://api.jquery.com/jquery.get/) when I saw $.get, when $ was just bound to getElementById~~ Switched back per @vandre request.

I look forward to any response.
Looks good! Thanks... I'll probably merge it this weekend after I have some
time to test it.

I see that you have a branch for transaction filtering... I also thought
about adding this feature but I'm very particular about UI design and UX
and I'm still undecided about what the best approach is to surface this
feature.  I would want to add more value to it, not just clone what
adotland did with Mint date range extension
 On Jun 10, 2014 8:51 PM, "Eric Clymer" <notifications@github.com> wrote:

> In Global.js:
>
> > @@ -1,19 +1,14 @@
> >  //Utility methods
> >  $ = document.getElementById.bind(document);
> > -$.get = function (url, callback) {
>
> Okay. I switched it back to use $.get.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/vandre/mojito/pull/2/files#r13628793>.
>