Raise requirejs compilation errors and exit from node with code 1

This provides better feedback when errors are encountered instead of
raising the more dubious "Cannot compute digest for missing asset".
Addresses #108 #93
Merge pull request #110 from negative/fix-missing-asset

Raise requirejs compilation errors and exit from node with code 1
Fix for overriding assets with combined versions in Rails 4.0 - fixes #137
Fix Sprockets check
Updated Almond to 0.2.5 and Require to 2.1.8.
Merge pull request #138 from andyjeffries/master

Rails 4 combined asset loading now overloads existing combined assets
Merge pull request #141 from skinnyfit/fix_sprockets_check

Fixes assets:precompile for new Rails 4 apps: fix Sprockets check
Merge pull request #142 from jankeesvw/master

Updated Almond to 0.2.5 and Require to 2.1.8.
Inline the ruby_rake_task helper, which is no longer available in Rails 4
Revert the previous commit and backport the ruby_rake_task method

It is better that requirejs:precompile:all runs in a fresh Rake process, so as not to clobber the parent Rake process' environment.
supports rails' relative_url when building baseUrl for requirejs
Updates require.js / r.js to version 2.1.10.
Adds uglify2 to build config whitelist.
Move initialization of the Config instance into the "config.before_initialize" block
Fix Rails 4.1.0 issues correctly
Don't force a specific rbenv Ruby version on the user
Updates LibVersion to 2.1.10.
Merge pull request #2 from gcirne/uglify2

Updates require.js / r.js to 2.1.10 adding support for uglify2
Fix unit tests
Exclude fallback paths when compiling with r.js, as they don't make sense for compilation purposes and cause r.js to choke