Clean up child processes on exit (#8)

fixes region still being active even if peek was toggled

fixes toggle-peek not un-peeking

improves help for -t, --toggle.

adds ability to completely hide the window using -P, --toggle-peek.

improves PKGBUILD for archlinux

ensure the window still exists

don't rely on stdin for --signal

add -w, --wait so we can wait for a window

delete pid file only if it exists

docstrings

CAPS ALL THE THINGS! (at least all globals)

fixed required arg check

README tweaks

added arch PKGBUILD