Add public:
 * has_type()
 * get_field()
 * get_enum()
 * enum_from_alias()
 * get_params()

Update documentation for ParamsType.

Add public: fromalias(), has_alias().

Update documentation for enumeration types.

Implement new op param type `EnumType`

Updated numpy as np #4218

Fix memory leak

Remove the old backend and all of its tentacles

It seems sphinx 1.5.1 is not available for Python 3.3.

Updated numpy as np #4218 

Use expm1 for elu