Add prechew data functions
Create derived slices!

Seriously, this is awesome. In your dataset definition, you can define
new slices by aggregating other slices. In fact, I added a dependency
graph so that you can derive slices from derived slices and it'll all
work out.

TODO: Allow WHERE clauses
Merge pull request #29 from marcesher/master

Mongo Integration Tests
Allow for filtering when creating derived slices
Added name and description of slices to API pages
Merge from master
Fixed broken integration tests
Merge pull request #30 from cndreisbach/aggregated-slices

Aggregated slices
Updated HMDA dataset to build multiple versions, keep correct order
Add Drakefile for manipulating HMDA data
Converted HMDA data manipulation completely to Drake
More HMDA lookups
Converted to use Drakefile
Two-step data loading: tables, then slices
Added agent error handling for table loading
Run Drakefile if it exists on load
Removed "cleaned" version of HMDA in expectation of future development
Added consumer complaint database

* Still need to add dates as a type
* Fixed really tricky bug with false in WHERE queries
Only load integration_test dataset in testing
Prevent non-existent Drakefiles from throwing errors