add styling for image request form
add bottom margin to prevent form from running into bottom of page
add Chosen jquery plugin for tag selection
add model and collection for Tags
fetch tags in Image Request Page
add bootstrap styling for chosen and define custom path variables

Need to pull in the bootstrap-sass repo because bootstrap-chosen
depends on variables defined in it.  We also needed to let bootstrap
and chosen know the path to their respective images.
convert select box to chosen multi-select
remove stylings from html that were rolled into app.scss
add key and placeholder text, improve styling