Remove `squeel` gem

Incompatible with Rails 4.1. Extract method object to query users by
full name, first name, last name, email and login. Add sanitization of
query passed from controller.

Update test assertion for querying users by full name.
Update to Rails 4.1

Includes updates to:
* shoulda-matchers
* simple_form
* haml-rails
* guise
Upgrade to Rails 4.1

* Remove `squeel` as a dependency
* Update Rails, simple_form, shoulda-matchers, haml-rails and guise