init Environment object

- this env is the generator handler and responsible of managing the
  entire lifecycle of executing generators

- added path manipulations methods

- paths / lookups can be used to specify specific loadpaths (npm
  packages, custom lookup, etc.)

Add Environment#help()

Add register and namespaces API, update help output

Add get, create, run API

Hoist up events from generator to environment

Add api to lookup generators and alias them

Add underscore.string API as generator method

Add prompt API

Init file API

Add glob and plugin API. Make angular generator test

- probably too much for a single commit. will prob rebase
- still need to figure out the strategy to test out existing generators,
  will prob add each as devDependencies

add bin file mapping yeoman-init command
detect generate name with "/", trigger npm install to get locally
init documentation
test - all passing
test - conflicter module