Meta seo 2

Refactored meta-data as part of API data
* meta-data is now a serializer field, keyword arguments define where the data source is. If the keyword argument is a callable on the model, that value will be returned.
* Bluebottle tests pass for python 2.7+. Import issues in 2.6.
* data transform 'object' added to read out the meta_data object
* registered meta_data as model field in Ember
* registered ember-meta to run after each navigation step and modify the meta-data (title, description, keywords, image, url)