Change RSS content type & use absolute URL in meta

no issue

- changes the content type for the RSS feeds from text/xml to
  application/rss+xml
- changes the link rel=alternate tag to use an absolute URL for the feed
  in the blog meta data
Add initial client unit test.
Merge pull request #4527 from rwjblue/unit-tests

Add initial client unit test.
Dynamic Titles in Ghost Admin

- Every route can set a title token that is combined with the blog’s
title, resulting in titles like ‘Content - Test Blog’.
- Subroutes are supported (‘Settings - General - Test Blog’)
- The blog’s name is applied to and taken from the `config` object to
spare Ember a REST call via `store.find(‘settings’)`.
- Tests have been changed to test for the new titles.
- The initially proposed solution
(https://github.com/paddle8/ember-document-title) doesn’t play nice
with EAK, which is why I went with this solution
(https://gist.github.com/machty/8413411) by Ember.JS core dev @Machty.
Merge pull request #4522 from felixrieseberg/iss4487

Dynamic Titles in Ghost Admin
Merge pull request #4518 from ErisDS/rss-fixes

Change RSS content type & use absolute URL in meta
Cleans up HTML data attributes on body in default.hbs

closes #4485

- removes data attributes used on body in default.hbs
- introducs new way to generate configuration throught meta tags
- config initializer consumes configurations from the meta tags using parser