Feature: Add automated git repo creation and commits

This change is necessary so that a new project will have
a git repo with a rough-draft branch with commits after adding
each configuration file.

Add git_commit, git_repo, and git_finalize methods to EmberBuilder

__note__: methods are built using system calls to git as Thor does not
have a git method built in.
Feature: Add setup script to finalize setup

This change is necessary so that project is all set up

Add setup_script and setup methods to EmberBuilder and
call them from EmberGenerator
Refactor: Change back tick git calls to use the Thor run command

This is so that the interface to git calls is more sematic and more
consistent with the rails generator

* Added a git method that implements the Thor run command
* Call git method as `git "<git commands>"`
Refactor: Add a file name to the git_commit arguments

This is so the script output is more informational and the `git add` command
is more precise, i.e. instead of calling `git add --all`, one can call
`git add <filename>`

* Added an additional argument to git commit: `def git(file, message)`
* Calls now look like `git_commit(file_foo, message_foo)`
Refactor: Move calls to gitignore and readme from EmberGenerator to EmberBuilder

This is because the `.gitignore` and `README.md` are part of the initial commit,
so it makes more sense to include them in the `app method` of `EmberBuilder`
Bug: Fix setup script call to run from the installed directory

This is necessary because the setup script was not being run
in the new project directory, rendering it effectively useless.

* Wrap the Thor `run` method in an `EmberBuilder#run` method
* `Dir.chdir(app_name)` before calling super (`Thor#run`)
Refactor: Revert git_commit so that it doesn't take a file argument

This is so that when multiple files are added by EmberBuilder they can be git added
with a one-line command. It is also more consistent with RailsBuilder git_commit
interface
Feature: Add ember-cli development dependencies

Add the following to the EmberBuilder and EmberGenerator
* broccoli-sass
* broccoli-coffee
* broccoli-ember-script

Add the following to the ember setup script so new developers can
pull down and run the setup script and start coding

* `npm install -g ember-cli`
* `npm install -g bower`
* `npm install`
* `bower install`
Feature: Enable prepend_file command to be run from the correct directory

Added an EmberBuilder#prepend_file method that includes `Dir.chdir(app_name)`
before calling super (Thor::Actions::prepend_file)
Refactor: Send both STDOUT and STDERR from overcommit command to /dev/null

This is because overcommit does not have a way to selectively install only
the pre-commit hook
Refactor: Split shared/overcommit.yml into separate ember and rails files

This is because the overcommit.yml configuration is different between
ember and rails
Chore: Include scss-lint check for aligned property values

This sccs-lint feature is not included in the current version (v0.24.1).
So when the feature is released it should start working as per the
scss-lint.yml configuration