Update to react-source 0.11

Als re-ran bundle exec rake appraisal:install
Add Rails 4.1 to test list

Closes #38
Create a installation generator

[Heavily based on the ember.js bootstrap generator]

Running rails generate react:install will append the basic require directives
to application.js

Possible avenues for upgrades:

  - allow for files with arbitrary names ("mycomponents.js" instead of
    "application.js")

  - allow for files with different extensions ("application.js.coffee"
    instead of "application.js")