Componentizes alerts

Moves alert box styles to a component partial and creates /components/
directory for modularizing components into individual partials. Also
adds alerts to style guide.
Updates asset gems

Updates several asset gem dependencies.
Updates font-awesome gem

Updates font-awesome gem to latest version and changes “icon” variable
in views to “iconclass” as “icon” is a reserved method name used by
font-awesome-sass (boo for this being global! >:( ).
Updates pagination spec

Updates pagination spec to handle use of font awesome chevron fonts for
previous/next buttons.