Add powerline release 1.0

Subj.
All of the others changes are fantastic, Nikolai.

However, **this line is problematic.** `--`-prefixed command-line options are GNU-specific and hence fail under BSD (e.g., [Gentoo Prefix](https://www.gentoo.org/proj/en/gentoo-alt/prefix) on Mac OS X, [Gentoo/FreeBSD](https://en.wikipedia.org/wiki/Gentoo/FreeBSD)). For compatibility, `-`-prefixed command-line options are *always* preferable. This line should probably read:

    sed -i -e '/sys\.path\.append/d' "${S}"/plugin/powerline.vim