Adds layer selector
Adds layer_selector
Merge branch '2.1' of github.com:CartoDB/cartodb.js into 2.1

* '2.1' of github.com:CartoDB/cartodb.js:
  multilayer example
Removes test
Removes test
Fixes misspelling
Adds methods for enabling and disabling the scrollwheel. Sets the scrollwheel option in the vis file
Add a test for the scrollwheel
Fixes a bug that disabled the scrollwheel in leaflet when the param wasn't set in the url
fixed interactivity
merged changes
merged with 2.1