House cleaning

* Removes several asset files, both javascript and stylesheets. This way
  we can easily identify where is our frontend code coming from.
Handlebars helpers in coffeescript

* Turns our custom handlerbars helpers into coffeescript code.
* Removes commented block from backbone-overrides files.
Converts CustomerFullView into a Layout

* Converts CustomerFullView into a Marionette.Layout
* when CustomersApp.Show.Controller.showCustomer() function is called,
  the new layout is instantiated as well as two views: CustomerFullView
  containing the model requested and also a CompositeView named
  TransactionsList that receives the model transactions as collection.
Converts Customers List view into a Layout

* Customer List view page is now a Marionette.Layout.
* Original CustomerList view is rendered inside a region on the
  List.Layout view.
Adds Empty Customers view to CustomersApp.List view.
Adds a new region to CustomersApp.List.Layout

* new region on CustomersApp.List.Layout will hold a form to add a
  new customer when clicking the 'Add Customer' button.
* creates the CustomersApp.New module to hold all logic regarding
  adding customers.
Upgrading to Rails 4

* Changes gem versions.
* Ran rake rails:update to aid in migrating application.
Fixes Api::Controllers from Rails upgrade.

* Edits specs and controller behavior for:
  * Api::CustomersController
  * Api::PaymentsController
  * Api::PurchasesController
  * Api::RegistrationsController
  * Api::AuhtenticationController
Fixes models specs.

* Fixes specs for: Purchase, Customer, LineItem models.
Removes deprecation warnings from Rails 4 upgrade.

* Edits default_scope declaration on Transaction model.
* Edits config.secret_key_base token on initializers
Adds Unicorn webserver
Merge pull request #12 from antillas21/develop

Develop