make 'alias' check for recursive calls and insert 'command'; update docs, fix #486
re-enable tests that were accidentally disabled in 0b1e3718
Remove origin/HEAD lines from __fish_git_branches.

Related discussion:
http://stackoverflow.com/questions/354312/why-is-origin-head-shown-when-running-git-branch-r
fix bug in export status of universal variable assignment
really fix bug in export status of universal vars; add tests for that bug