Merge pull request #8 from wpeterson/master

Emoji Indexing and Image Replacement
Adds rail integration via railtie and installer

* rake emoji:install_assets copies all images in
* Default emoji config via `initializer`
* Register rake task via `rake_tasks`
README for install/config w/ railstie

Adds details about running asset install rake task and moves configuration usage to the end (since it should work by default now).
Use escape_utils if available, fall-back on CGI.