pypy test fixes for issue #616 and #617

[qwcode]

this handles pypy test failures for #616 and #617
#616:

the fix is to skip testing the user scheme in pypy. --user installs are broke in pypy.
previous to skipping the tests most of the errors were related to improperly locating 'no-global-site-packages.txt', which is related to the fix for #617. see below.
#617

the fix I made is to add a workaround to compensate for this bug: pypa/virtualenv#306
I think virtualenv misreports the lib_path for pypy

[travisbot]

This pull request passes (merged 483adaa into 0fcfe0f).

[qwcode]

this busted other pypy tests.
so, I fixed env.lib/env.lib_path for pypy, but that now throws off the site-packages definition which doesn't apply for pypy
`self.site_packages = self.lib/'site-packages'

[qwcode]

don't think you noticed my comment about how this busted other tests.
I pushed up a fix right after you merged.

[qwcode]

let me do a another pull to get that commit in

[pnasrat]

Yeah sorry - merging before coffee.

[qwcode]

just posted another pull, and will wait to confirm failures are down to the 2 remaining ones that I expect before merging.
(the 2 I haven't looked at)