Upgrade jquery-rails gem

* Upgrade from 2.0.2 to 3.0.4
* Start from a newer jQuery version (1.10.2)
* Supported by Bootstrap 2.3.2
Remove jquery_ujs include from application

* We aren't using these features yet
Add Jasmine gem and generate scaffold

* Add 2.0.0 rc3 gem and run 'rails g jasmine:install'
* Jasmine will be used for JavaScript feature testing, with a
dependency on PhantomJS
Toggle 301 and 410 fields when editing a mapping

* Create a GOVUK.Mappings.edit function which hides/shows the
appropriate form fields on load, and whenever the http status changes
* This simplifies the form and clarifies which fields are needed for
which http status type
* Use fieldsets to determine which fields to hide/show, using js
prefixed class names
* Add Jasmine test spec
Add Jasmine tests to default rake task

* Run JavaScript tests by default
Add steps for mapping field visibility

* Include poltergeist to allow cucumber to run PhantomJS (and hence
JavaScript)
* Completes integration testing for dynamic mapping fields
Merge pull request #36 from alphagov/dynamic-mapping-fields

Hide irrelevant URL fields in Mapping form [57569274]