Prepend / append placeholder to input

Conflicts:
	app/assets/javascripts/lalala/modules/init.module.js
Documented input_group module
Use input_width variable to size input-group
Removed new page button from header in pages views
Button New in header hidden on edit view of model
Added pre & post fields to an article in dummy app

Conflicts:
	test/dummy/app/admin/articles.rb
	test/dummy/db/schema.rb
New DB schema