chore(Grunt): switch from Rake to Grunt

[IgorMinar]

Migrates the Angular project from Rake to Grunt.
Benefits:

• Drops Ruby dependency
• Lowers barrier to entry for contributions from JavaScript ninjas
• Simplifies the Angular project setup and build process
• Adopts industry-standard tools specific to JavaScript projects

BREAKING CHANGE: Rake is completely replaced by Grunt. Below are the deprecated Rake tasks and their Grunt equivalents:

rake --> grunt
rake package --> grunt package
rake init --> N/A
rake clean --> grunt clean
rake concat_scenario --> grunt build:scenario
rake concat --> grunt build
rake concat_scenario --> grunt build:scenario
rake minify --> grunt minify
rake version --> grunt write:version
rake docs --> grunt docs
rake webserver --> grunt webserver
rake test --> grunt test
rake test:unit --> grunt test:unit
rake test:<jqlite|jquery|modules|e2e> --> grunt test:<jqlite|jquery|modules|end2end|e2e>
rake test[Firefox+Safari] --> grunt test --in=[Firefox,Safari]
rake test[Safari] --> grunt test --in=[Safari]
rake autotest --> grunt autotest

NOTES:

• For convenience grunt test:e2e starts a webserver for you, while grunt test:end2end doesn't.
  Use grunt test:end2end if you already have the webserver running.
• Removes duplicate entry for Describe.js in the angularScenario section of angularFiles.js
• Updates docs/src/gen-docs.js to use #done intead of the deprecated #end
• Uses grunt-contrib-connect instead of lib/nodeserver (removed)
• Removes nodeserver.sh, travis now uses grunt webserver
• Built and minified files are identical to Rake's output, with the exception of one less
  character for git revisions (using --short) and a couple minor whitespace differences

Closes #199