* Removes future from python-exp v3 sample
* Removes future from python-exp v2 sample
* Deletes future from remaining python-exp files
* Removes six from python-exp templates
* Removes six from python-exp samples
* Removes mock from python-exp
* Python-exp switched to py3
* Removes python 2.7 for python-exp ci testing
* Requires python>=3.3 for python-exp
* Reverts unnecessary changes to two templates
* Use AttributeError instead of ApiKeyError because that's what the hasattr builtin function uses
* Use AttributeError instead of ApiKeyError because that's what the hasattr builtin function uses
* fix unit tests
* create ApiAttributeError exception
* fix formatting
* run samples scripts
* Adds composed model support for allOf oneOf anyOf
* Moves discriminator into discriminator() class method, adds test_deserialize_lizard, adds setting discriminator using allOf schema