upgrade virtualenv to latest version (1.10.1)
Merge changes from @raphigaziano - upgrade virtualenv to latest version (1.10.1)

Merge branch 'virtualenv-1.10.1' of git://github.com/raphigaziano/virtualenv-burrito into raphigaziano-virtualenv-1.10.1

Conflicts:
	test_download.py
	versions.csv