Check for duplicate cubes within namespace
Eat the is_model_provider option
added Cube.basename
renamed extensions class Namespace to ExtensionsNamespace
All cubes are now stored in store's namespace by default; added option "lookup_method" with global/recursive values
Use default namespace instead of "default"; added a bit of debug log
Extensions refactoring: unified way of getting an extension; new base class "Extensible"

Removed multiple extension retrieval methods and replaced them with
common `extensions.TYPE(NAME, …)` as in `extensions.store(“sql”, …)`.
Since now extensions can provide info without instantiation: added info to backends and removed flag is_model_provider
Allow aggregate names not to be specified
Beginning of browser abstraction: separated provide_aggregate() from aggregate(), aggregate() now supports prepared arguments for provide_aggregate()
[backend-ga] Removed preparation code which is now in the browser superclass.
mongo2 backend properly identifies time dimensions
more resilient is_date_dimension for mongo2 backend
Fix typo in sample code.
do not lowercase field names in /facts arg; basic but incomplete
improvement of MixpanelMapper; use cube basename
Merge pull request #160 from sfermigier/master

Fix typo in sample code.
Keep store in the browser
Refresh the SQL aggregate computations for new browser objects
Fixed the ini with the new format

The hello world example was failing with unable to retrieve "model".
Merge pull request #162 from samof76/master

Fixed the ini with the new format