Refactor data-source factories.

[stevemacn]

The current model for data cached from the data-sources is
very twitter-centric. Project deadlines prevented me from going
back to fix this but moving forward fixing this is essential. A
simplified model and simplified factory will make it trivial to add
new data-sources and make maintenance easier.

What needs to happen:

1. Query parameters for data-sources should be stored in an array of mixedType and variable size.
2. Query parameters can therefore be different depending on data-source.
3. Query parameters are compared to the cached parameters (if they are less than, retrieve from cache).
4. Streams.js - the factory should be streamlined to handle all the cache comparisons rather than
   deferring this responsibility to each of the individual data-sources. (This should be overridable).