Restore zsh ctrl-p

Unite is just extremely slow. Takes several minutes to actually return
a complete set of results.

There is no point in even trying to use something that slow. I also have
not seen a single example of 'unite is teh awesomes' that actually
justifies using it over ctrl-p. I have seen several blog posts that
claim that it is 'teh awesomes' with no concrete examples. Fuck that
noise.