Prism Browse view

Adds a prism browse view to the controller; and a view for it
Browse Page Update
fixed browse page borders
flash message fix
fixed merge errors in header
Merge branch 'develop' of github.com:scholarslab/prism into develop

Conflicts:
	app/assets/stylesheets/media/_screen.scss
	app/controllers/prisms_controller.rb
	app/views/layouts/_header.html.erb
	app/views/pages/about.html.erb
	app/views/prisms/highlight.html.erb
	app/views/prisms/index.html.erb