fixed type in controller.rst documentation
updated model.rst documentation to use mamba.enterprise instead of storm.locals
added Expr to mamba.enterprise
documented multiple database connections
fixes to documentation
fixed wrong .. soucecode tag in documentation
Fixed duplicated index name mentioned in #51.
Merge pull request #85 from nicholasamorim/index_name_fix

Fixed duplicated index name mentioned in #51.
Added support to fields and exclude when serializing to dict or json
Removed clutter and added parameters in the function docstring.
Added documentation on serialization with fields and exclude.