Add component generator

Will be able to add the component after the project was created.

how to use:

```
$ padrino g project simple_project
$ cd simple_project
$ padrino g component
Usage:
  padrino-gen component [options]

Options:
  -r, [--root=ROOT]              # The root destination
                                 # Default: .
  -a, [--adapter=ADAPTER]        # SQL adapter for ORM (sqlite, mysql, mysql2, mysql-gem, postgres)
                                 # Default: sqlite
  -d, [--orm=ORM]                # The database engine component (activerecord, couchrest, datamapper, minirecord, mongoid, mongomapper, mongomatic, ohm, ripple, sequel, none)
  -t, [--test=TEST]              # The testing framework component (bacon, cucumber, minitest, riot, rspec, shoulda, testspec, none)
  -m, [--mock=MOCK]              # The mocking library component (mocha, rr, none)
  -s, [--script=SCRIPT]          # The javascript library component (dojo, extcore, jquery, mootools, prototype, rightjs, none)
  -e, [--renderer=RENDERER]      # The template engine component (erb, haml, liquid, slim, none)
  -c, [--stylesheet=STYLESHEET]  # The stylesheet engine component (compass, less, sass, scss, none)

Description:

        padrino-gen component add components into a Padrino project

Current Selected Components:
  orm         none
  test        none
  mock        none
  script      none
  renderer    slim
  stylesheet  none
```