Special case os.devnull for PIP_CONFIG_FILE to mean 'no config file'
Merge pull request #1544 from pfmoore/devnull

Special case os.devnull for PIP_CONFIG_FILE to mean 'no config file'
'pip wheel' should download wheels, when it finds them

Conflicts:
	pip/commands/wheel.py
	pip/download.py
	pip/req/req_set.py
	pip/wheel.py
when file urls have hash fragments, check it
fixes for downloading wheels (Issue #1112)

Conflicts:
	pip/req/req_set.py
cherry-pick fixes
update changelog
pip docs refactor
deprecate --build and --no-clean
Merge pull request #1574 from qwcode/deprecate_build

deprecate --build and --no-clean
Ensure wheel-Version is compatible with pip
Merge pull request #1581 from dstufft/test-wheel-version-1.5.x

Test wheel version 1.5.x
Don't pass a unicode __file__ to setup.py on Python 2.x
Upgrade six to 1.5.2
Merge pull request #1583 from dstufft/non-unicode-file

Don't pass a unicode __file__ to setup.py on Python 2.x
Add changelog item
Bump version and mark release date in the changelog
Merge branch '1.5.X'

Conflicts:
	CHANGES.txt
Merge branch 'master' into develop

Conflicts:
	CHANGES.txt
	docs/configuration.rst
	docs/cookbook.rst
	docs/reference/pip.rst
	docs/usage.rst
	pip/__init__.py
	pip/commands/install.py
	pip/commands/wheel.py
	pip/req.py
	pip/wheel.py
	tests/unit/test_wheel.py