Add command-line component generator

Adds a generator that scaffolds up a complete, but minimal, component
using JSX and a propTypes hash.

Run `rails generate react:component --help` for usage notes.
- Enable emitting warnings by default
- `File.exists?` is deprecated, changed to use `File.exist?` instead.
- Fixed react renderer and view helper to not throw ambiguous arguments warnings, when asserting data using regex arguements.
Document the command line component generator
Remove deprecated calls from README.md
Merge pull request #100 from vipulnsward/100-fix-warnings

Fix warnings
Merge pull request #114 from conceptualitis/master

Remove deprecated calls from README.md
Merge remote-tracking branch 'upstream/master' into component-generator
Changes to work with React 0.12 and follow @zpao's recommendations
Fix outdated README notes on the component generator
Merge pull request #96 from xionon/component-generator

Add command-line component generator
- Rearrange `React::Renderer` methods and move non-public methods to private
- Make use of `default_pool_options` hash, instead of hard-coding magic numbers when initializing `ConnectionPool`
- Use hash.except! instead of manually deleting hash options.
- No need to explicitly check if options[:prerender]'s value is true
Merge pull request #99 from vipulnsward/1-refactorings

Minor refactorings
From http://edgeguides.rubyonrails.org/4_2_release_notes.html#action-pack
> When calling the process helpers in an integration test the path needs to have a leading slash.
> Previously you could omit it but that was a byproduct of the implementation and
> not an intentional feature.

- Fixed all get requests to have a forward slash to fix failing tests on rails 4.2
Merge pull request #137 from vipulnsward/fix-tests-on-rails-4-2

Fix tests on rails 4.2
Adding example about how to disable automatic unmounting of components [ci skip]