Merge pull request #6 from larsbutler/run-calc

Run calculations via REST API (initial sketch)

[r=matley] [f=*1206913]
Merge pull request #7 from larsbutler/run-calc-2

Run calcs, part 2

[r=matley] [f=1206913]
engine/views:

Removed a decorator which was reinventing the wheel and replaced it
with a django built-in equivalent (for limiting request types to views
and returning a 405 if the request type--POST, GET, etc.-- is not
supported).
engine/views:

Return 404s (instead of empty data sets) where there is no calculation
or result data.
engine/views:

Pyflakes cleanup.
engine/views:

Instead of a 501, return a 404 if an export type is not supported.