fix(remote): don't close stdout on fetch/pull
fix(remote): don't close stdout on fetch/pull

Reverted changes of `fe2fbc5~2`.

This caused `git-pull` to error, which now actually results in a fatal
error while fetching or pulling. Previously we simply didn't check
for this issue.

Now we are back to a `poll` based or threaded concurrent reading from
stdout and stderr to prevent a git process deadlock, and the
aforementioned error.

Related to #297

nvie/GitPython,StyXman/GitPython,gitpython-developers/GitPython,avinassh/GitPython,beni55/GitPython,jeblair/GitPython,expobrain/GitPython,pengshp/GitPython,manasdk/GitPython,dpursehouse/GitPython,h4ck3rm1k3/GitPython,StyXman/GitPython,manasdk/GitPython,zsjohny/GitPython,pengshp/GitPython,gitpython-developers/gitpython,pengshp/GitPython,breavo/GitPython,expobrain/GitPython,cdht/GitPython,roidelapluie/GitPython,ghtdak/GitPython,beni55/GitPython,ghtdak/GitPython,nvie/GitPython,h4ck3rm1k3/GitPython,bwrsandman/GitPython,cdht/GitPython,gitpython-developers/gitpython,breavo/GitPython,avinassh/GitPython,StyXman/GitPython,jeblair/GitPython,avinassh/GitPython,cdht/GitPython,gitpython-developers/GitPython,roidelapluie/GitPython,dpursehouse/GitPython,zsjohny/GitPython,bwrsandman/GitPython,bwrsandman/GitPython,zsjohny/GitPython