Try out OmniJSON for amara's JSON inclusion logic

[uogbuji]

Amara includes logic to try to find and provide a JSON library, but it's not as well-studied as other alternatives such as AnyJSON and OmniJSON. The latter has the advantage of bundling Ippolito's simplejson for a built-in default. OmniJSON is also designed to be "vendorizable," meaning it should be easy to bundle in thirdparty, or we could also just include it in the setup.py prerequisites.