store static assets under version control

[erikj]

static in Django terms, assets in Rails.

store JavaScript and CSS libraries w/ the application under version control, so that they don't always float up to the latest version when they are installed via bower.

currently acquired via django-ncharts/get_static_files.sh wrapper script, which gets all assets via bower install, except Highcharts assets, which are acquired via wget

update docs accordingly.