Updated README.md

Updated README.md to correct `{{> menu}}` helper references
fix page_url helper for ghost 0.5
Merge pull request #37 from epistrephein/master

fix page_url helper for ghost 0.5
Add Google Tag Manager partial

Google Tag Manager enables the configuration of multiple Analytics tags
without the need of changing the tracking code.

Following the same approach used for comments and the menu, a
'google-tag-manager' partial was created and inserted in default.hbs,
disabled by default.
Enable Google Tag Manager
Enable Disqus
Fix navigation menu margin for last child
Disable responsiveness of navigation menu items
Enable menu with Social Networks links