Log Message:
Update to 1.6.0:

1.6.0
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* Strip comments in requirements files

1.5.0
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* Handle git being entirely absent
* We require the use of setuptools
* Fix retrieval of commit data and most recent tag

1.4.0
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* Fix docs for environment markers in extras
* Export ChangeLog and AUTHORS in install
* Updated from global requirements
* Updated from global requirements
* Show how long the git querying takes
* Add wsgi_scripts support to PBR
* Updated from global requirements