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.
special case custom readline on darwin

avoids readline being installed to the wrong location.
pythonX.Y symlinks should be made on all platforms

The comment on line 1412 ("Some tools depend on pythonX.Y being
present") is accurate on all platforms, but the block of code that
ensures that pythonX.Y is present is inside a conditional that checks
"if '.framework' in prefix".

This commit moves the code out of the conditional so that it applies on
all platforms.
Use ctypes to support paths with spaces rather than pywin32
Refresh bundled copy of distribute (now at 0.6.30).

This fixes #301 and integrates another local change we had made to
distribute_setup.py: https://bitbucket.org/tarek/distribute/issue/328/
Don't pass unexpected arguments when installing from a source dist.

This used to be silently ignored, but not since
https://bitbucket.org/tarek/distribute/changeset/1c01b2620acb553fc101e3b5c8d0540d204d79a4/
Add one integration test to exercise most of the code.
Restore PyPy compatibility.

PyPy's interaction with virtualenv is strange and should probably
be rethought.
Merge pull request #346 from g2p/develop

Refresh distribute (now at 0.6.30), add integration tests, fix distribute call
Merge pull request #345 from pfmoore/use-ctypes

Use ctypes to support paths with spaces rather than pywin32
Merge pull request #337 from minrk/readlinepr

special case user-installed readline on darwin
Update docs
Ensure all permutations of version name exist

This ensures that all required names are symlinked to py_executable.
Note that it does not do this on windows, as I am not sure what the
requirements are there (pythonX.Y.exe?), and it didn't do this
previously anyway.

This will fix #347 as well as #341.
Edited the release notes.
Use extended syntax of `set` command which handles special characters in variable's value. Fixes issue #351
Merge pull request #350 from g2p/develop

Edited my part of the release notes.
Merge pull request #352 from piotr-dobrogost/develop

Use extended syntax of `set` command in activate.bat/deactivate.bat batch files.
Refactoring to show logic better
Merge pull request #354 from piotr-dobrogost/activate_deactivate_refactoring

Refactoring to show logic better
Add a --setuptools option (which implicitly adds $VIRTUALENV_SETUPTOOLS)
envar, for overriding any default use of distribute.  No-op in Python 3.