zshrc: Replace tmux aliases 'tn' and 'ta' with a single 't' function
zshrc: Remove tree alias to force ascii charset.

It can be added to .zshrc-local on systems that need it.
tmux.conf: Increase escape-time to 50

Cygwin always has problems with a value of 0, and sometimes has problems
with 1. Using 50 should give a good, but minimally noticeable safety margin.