Merge pull request #1 from radcliff/models

Models
makes http request for USA shapefiles and unzips
seeds regions, states, and counties; added index on states on name; changed drought_shapes :shape geometry from multi_polygon to polygon
Merge pull request #2 from radcliff/seeds/states+counties

Seeds/states+counties
added ApplicationHelper
added rake task - grabs drought data from USDM, clips it + shovels it into database; changed geometry type of drought shapes to generic "geometry"; added index on drought shapes on states
Merge pull request #3 from radcliff/seeds/drought

Seeds/drought
changed column type from polygon to geometry in original migration
further modularized helpers: application helper => geojson helper + topojson helper; added topojson gem
requests for state drought data willl render a topojson response
trivial changes
Merge pull request #4 from radcliff/controller/droughtshapes

Controller/droughtshapes
added support for :geo parameter, if "true" response will be in geojson
Merge pull request #5 from radcliff/controller/droughtshapes-geo

added support for :geo parameter, if "true" response will be in geojson
added AboutHelper; requests without parameters respond with about json
Merge pull request #6 from radcliff/controller/droughtshapes-about

added AboutHelper; requests without parameters respond with about json
update readme; fixed properties argument in geojson helper; trivial changes
added gem: execjs
added ExecJS; added single-file topojson library; evaluates geojson to topojson in TopojsonHelper and returns result