Introduce a .gitignore to the project

Ignore grunt's node_modules
Ignore the concatenated version of wsumed.js
Add a minified version of all extra D3 related scripts

We have a bunch of scripts in use that are not being modified. This
introduces a quick grunt process. This isn't necessarily meant as
a long term workflow, just something to save on immediate page
views.
Load the single minified script in most cases

This saves 8 HTTP requests. :)
Merge pull request #7 from washingtonstateuniversity/grunt

[PR] Use Grunt to minify a production version of all (9) extra scripts