Added rails template generator

Adds all of the plumbing to support a .ts file template generator. In the spirit of maintiaining existing functionality, we do not default the default javascript generator to typescript. However, anyone can opt into this functionality by adding the following to their config/application.rb:

config.generators do |g|
  g.javascript_engine :typescript
end

Small fixes

Fixed incorrect value of register_mime_type

Sprockets 4 support

Added Sprockets 4 support. Thanks to @mihai-dinculescu.

Update to Typescript v1.6.2

Added incorrect file name output on TypeScript compilation error.

Updated version to 0.6.0

Updated version to 0.6.0 for using Typescript source 1.4.1.3