Adds :development and :test groups in Gemfile

* Lists additional gems used on development and test environments.
Installs RSpec

* Basic spec_helper config.
Adds strong_parameters gem

* Adds strong_parameters gem to Gemfile
* Adds initializer to user strong_parameters in every ActiveRecord::Base
  model.
* Disables whitelist_attributes, thus ActiveRecord models don't need
  to include attr_accessible.
Adds bcrypt to handle User.password encryption

* User model includes has_secure_password.
* changes users table schema to user password_digest as needed by
  ActiveModel::SecurePassword.
* Adds base spec for User model.