Add --no-setuptools and --no-pip options.

In specialised circumstances (e.g., when testing new versions of distribute
or pip) it can be useful to create a virtualenv which does not include these
packages pre-installed. Add options to specify that when creating the
virtualenv.
Merge branch 'release/1.8.4' into develop
Forgot to add this to the news.
Clear VIRTUAL_ENV environment variable. Fixes issue #9.
Upgrade the bundled copy of distribute to 0.6.32.

Prompted by https://bitbucket.org/tarek/distribute/issue/335/
Use pypy readline even on OS X

If the OS X special case is put in place for pypy
then the lib_pypy directory is not created, and pypy
will run without sys.prefix being set, which causes
virtualenv to fail to build.
Merge pull request #374 from ptone/pypy-fix

Fixed the name for the pypy include lib
Merge pull request #367 from g2p/develop

Upgrade the bundled copy of distribute to 0.6.32.
On multiarch-aware Debian/Ubuntu Pythons, plat-${sys.platform} does not point
to a valid sys.path entry.  Use sys.implementation._multiarch (Python 3.3+),
sys._multiarch (Python 2.7) where available, falling back to sys.platform for
non-multiarch aware Pythons.
Merge pull request #379 from warsaw/issue378

Fix for issue 378
Removed cygwin code enforcing a .exe extension.

It just causes more issues down the line.
Merge pull request #382 from nightpool/cygwin-exes

Removed cygwin code enforcing a .exe extension.

Later code that uses symlinks caused this to break.
Merged with upstream
Merge pull request #336 from pfmoore/disable-pip

Add --no-setuptools and --no-pip options.
Virtualenv is no longer in beta ;)
Merge pull request #386 from pombredanne/pypi_qualifiers

Virtualenv is no longer in beta ;)
windows test fixes
Merge pull request #391 from qwcode/win_fixes

windows test fixes
develop branch is 1.8.4.post1
upgrade to distribute-0.6.34