Objects as request parameters don't properly serialize in cache keys

[hazeledmands]

When you make a request like this:

var Derp = $cachedResource('derp', 'http://herp.com/derp/:id')
Derp.query({where: {createdAt: { $lt: 5 } } })

rght now we're ending up with keys like this:

cachedResource://derp/array?query=[Object object]

when we should have something like this:

cachedResource://derp/array?query={where:{createdAt:{$lt:5}}}

We need to be careful that the serialization scheme is deterministic (alphabetize keys, etc) so that the same query always uses the same resource.