Parallelize loading of datasets based off each file

* Trying parallelizing within each file first, which had good success
* Success when using pmap, which seems wrong
* Using agents, ran into issues on large datasets
* But agents worked well with multiple files

Idea for future:

* Parallelize by file if multiple files
* Else parallelize within file
Use clojure.data.csv instead of clojure-csv
Parallel loading of datasets is now the default
Pass callback name through to JSONP view
Added integration test for JSONP callback
Test JSON, XML, and JSONP responses
Return 400 response code if query is invalid
Run all tests during integration
Validate that limit has a maximum of 1000

Also, and bigger, moved all pre-Mongo validation into a separate namespace
Load records in batch instead of one-by-one
Merge pull request #24 from cndreisbach/jsonp-fix

Pass callback name through to JSONP view
Merge pull request #25 from cndreisbach/response-codes

Added 400 response code when a query is invalid
Merge pull request #26 from cndreisbach/limit-1000

Limit has a maximum of 1000
Merge pull request #22 from cndreisbach/parallel-load

Parallel loading of datasets