fix pexpect-3.0 compatibility for pytest's own tests.
(fixes issue386)
fix issue384 by removing the trial support code
xfail a test on pypy that checks wrong encoding/ascii (pypy does
not error out). fixes issue385.

also re-enable pypy tests in tox.
add missing importorskip
fix issue380 by making --resultlog only rely on longrepr instead
of the "reprcrash" attribute which only exists sometimes.
don't hide an ImportError when importing a plugin produces one.
fixes issue375.
internally make varnames() deal with classes's __init__,
although it's not needed by pytest itself atm.  Also
fix caching.  Fixes issue376.
fix ordering when mock.patch or other standard decorator-wrappings
are used with test methods.  This fixues issue346.  Thanks to
Ronny Pfannschmidt and Donald Stufft for helping to isolate it.