Merge pull request #5 from nyeholt/master

Metadata output changes
Extra attributes check for <meta> tag output
Updated extra attributes to allow for multiple field extensions
Merge pull request #6 from gheggie/master

Extra attributes check for <meta> tag output
Switched to using GridFieldExtensions module instead of Sortable Grid Field
Revert "Switched to using GridFieldExtensions module instead of Sortable Grid Field"

Gridfield extensions is 3.1 only...

This reverts commit 88f0cb30959c8e0df95df24ab1220a5d24441519.
Patched templates + code for 3.1 support
Merge branch 'master' of github.com:nyeholt/silverstripe-metadata