alias: make copy/paste with prompt work

For example:

    $ echo hello
    $ echo hi

Stolen from:
 https://github.com/jordansissel/dotfiles/blob/master/.zshrc
env: try to set GOPATH to the current directory

Stolen from @jordansissel
title: get job title when passing a job foreground

The code is adapted from:
 https://github.com/kejistan/acmdots/blob/master/zsh/title
title: keep using full command to display title
title: automatically compute a short title if possible