Added --root command line option, works the same as for distutils
Simple test to check --root option functionality
PyPy is special and overrides default distutils directory scheme, alter test to suit
Merge pull request #23 from dholth/wheel_build

Allow pip wheel --use-wheel
add --no-deps option to "pip wheel"
don't ignore building pip/setuptools/distribute
import check at 'pip wheel' command level is enough
Give wheels priority over sdists when installing
Merge pull request #25 from pfmoore/wheel_priority

Give wheels priority over sdists when installing
Added author name and description of changes
Merge pull request #693 from hetmankp/develop

Added --root command line option to give functionality equivalent to distutils --root
test readme update
link sort key as instance method; guard when link is InfLink
existing install has priority over wheels
correct extras syntax in docs
remove global command instances

Rework the way commands are defined, loaded and ran in pip:

 - Commands are instantiated on demand in pip.main().

 - A command 'registry' - mapping of command names to command classes in
   pip.commands.__init__.

 - Remove deferred command module loading.
add create_main_parser() and the '-V --version' option
add the base_parser argument to all Command instances
replace global OptionParser and refactor main()
make monkey-patching work again in tests/test_user_site.py

Monkey-patching 'pip.util.dist_in_site_packages' through
'sitecustomize.py' in 'tests/test_user_site.py' wasn't working unless
the fully qualitifed path to 'dist_in_site_packages' was
used.