Merge pull request #311 from trisweb/trisweb_2.3.1

Upgrade to 2.3.1 from official upstream.
instruct people to install after adding to Gemfile
add instructions for Rails 4 asset pipeline change
Merge pull request #317 from PatrickMa/master

#316 - Found a temporary solution, adding it to readme.
Move Rails 4 section after Rails section

To avoid confusion.