Add footnotes extension to showdown

refs 1318
- based on Markdown Extra https://michelf.ca/projects/php-markdown/extra/
- allows [^n] for automatic numbering based on sequence
Scroll post-item-view into view

Closes #3998
- Scroll the active post into view on page load
- If the active post changes and the newly active post is offscreen, scroll it into the middle of the screen
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
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.
Swap nav item & logo style order

Closes #4532

- Swaps the order of nav-item and .ghost-logo styles, as .ghost-logo was being overwritten by .nav-item, allowing a hover state
Add Labs, Nav & Grab icons

References #4535, #4534

- Add an Atom icon for Labs page
- Adds Compass and Grab icons for the Navigation page
Add Ghost version to config object.

No Issue
- Use Ghost version value that is already loaded instead of
  reading package.json from the filesystem and parsing it on
  every call into the configuration API.
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
Miscellaneous client cleanup

No issue
- Consolidate extension of Ember.Router.
- Remove unneeded local jshint flags and '_' as a global.
- Cleanup client README.md.
- Fix error message.
Merge pull request #4536 from PaulAdamDavis/labs-icon

Add Labs, Nav & Grab icons
Merge pull request #4533 from PaulAdamDavis/logo-no-hover-bg

Swap nav item & logo style order
Merge pull request #4538 from jaswilli/config

Add Ghost version to config object.
Merge pull request #4542 from jaswilli/misc-cleanup

Miscellaneous client cleanup
Cleans up HTML data attributes on body in default.hbs

closes #4485

- removes data attributes used on body in default.hbs
- introduces new way to generate configuration through meta tags
- config initializer consumes configurations from the meta tags using parser
- moves blog_title helper/value to be a property in a configuration api
Use non-deprecated moment.substract()

Closes #4545
- Go with subtract(value, string) instead of subtract(string, value)
Merge pull request #4548 from felixrieseberg/iss4545

Use non-deprecated moment.substract()
Generate sitemap files

Closes #623

- Add basic init and eventing scaffold
- Add sitemap-index.xml generation
- Broke out generators to individual files, added request handler
- Add page, author and tag xml files; add index mapping
- Add SiteMapManager unit tests
- Add Generators tests
- Cache invalidation headers for sitemap-*.xml
- Redirect sitemap.xml to index and rename to sitemap-index
- Handle page convert and publish/draft changes
- Add very basic functional test for route existence
- Add cache headers to sitemap routes
Prevent silent failures and recover after error.

Refs #4543
- Alway return model out of save handler so sub-classes which
  call this._super() on save have a model on success and failure.
- Always return resolved promise out of post slug generator.
- Test the errors object in the error notification helper to avoid
  throwing an unhandled exception and silently failing.
- Consider a post model "dirty" if it is in an error state.