Merge pull request #8 from oivoodoo/issue/7-model-scope

Use scope out for the model class
Bump gem version to 0.1.3
Add few things under the .gitignore
Fix the namespaced models for masquearades:

  - Now it's possible to use the models like this example ```Admin::User```:
  ```
  devise_for :admin_user, :class_name => "Admin::User"
  ```
  - Added spec to cover this things
Apply @bbuchalter for the class_name of the mapping
Merge pull request #9 from bbuchalter/master

Use mapping class name
Merge pull request #11 from oivoodoo/issue/on-namespaced-models

Fixing the issue on namespaced models.
Sign in user after masquerade