implement some prettyping-inspired display instead of textual

implement some prettyping-inspired display instead of textual

this is a first stab at porting "prettyping.sh" into noping. the idea
is to show a histogram of ping times instead of numerical values. with
some work, we could actually show both, but this focuses on
implementing the hard part (the histogram) properly.

it is very rudimentary for now:

 * the math may be wrong for the size of the bar, I was mostly in a
   rush to make unicode work and have something pretty quickly.

 * all hosts are on the same line: each should have its own line

 * the histogram should be displayed in a separate window

 * it should use background colors as well

 * it should fallback when the terminal is not unicode-capable

 * the scaling logic is fully automatic, which necessarily gives weird
   results at first

this requires switching to the ncursesw library and other unicode
ncurses hackery described in this post:

http://newsgroups.derkeiler.com/Archive/Rec/rec.games.roguelike.development/2010-09/msg00050.html

pretty ping is a awk/bash script, MIT-licensed, available here:

https://bitbucket.org/denilsonsa/small_scripts/src/tip/prettyping.sh