Prevents updating the graph when the percentage is NaN
Adds main_loader. Puts more_data div in to a Backbone class
Merge branch 'develop' of github.com:CartoDB/cartodb20 into develop

* 'develop' of github.com:CartoDB/cartodb20:
  fixed problem when there is no data for that key in local storage
  refs Vizzuality/cartodb-management#2626