mutt: document <esc>L hotkey
zsh: add e and la aliases

I originally saw 'e' in one of screencasts about git-annex (by Joey
Hess). It appeared to me right away that using single-letter alias for
an editor---a program that I fire up hundreds of times per day---must be
pure efficiency win. But for some reason, I didn't add it into my config
at the time. Well, better late than never!

Idea for aliasing "ls -a" to "la" came to me when I was looking through
Hess's 'home*' repositories where he keeps his configs. As most of them
are dotfiles, I had to specify the parameter all the time, which was
annoying. Let's see if this alias would survive in a long term.
irssi: install splitlong script