No capfd

Changes:

 * Factor out pytest's `capfd` in favor of my `capture_subprocess` function.
    * py.test -s output now shows what's going on as it happens
    * also lets me show commands that run during test, without screwing
    * this allowed me to put pypy support back in without deadlocks
 * Ensure that we don't use pip6, virtualenv12 quite yet (patch incoming)
derp