Issue title: virtualenv --distribute is deprecated
 Issue body: See https://github.com/pypa/virtualenv/blob/5016707a064745da3e4fdbd72edc534838862c96/virtualenv.py#L754

This affects `modules.virtualenv.create()`'s corresponding `distribute` parameter.

 Comments: 
 Comment 0: See also the description for the current latest distribute package: https://pypi.python.org/pypi/distribute/0.7.3

 Comment 1: I have a fix on a local branch. Just need to add some tests before creating a pull request.

 Comment 2: @s0undt3ch I have already created pull request to fix this and pyvenv issues. See #6034.

 Comment 3: Ok.

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