~/.config/taffybar: Add memory usage widget.

Surprisingly, only calling pollingLabelNew doesn't do the job, we have
to call Graphics.UI.Gtk.widgetShowAll, too.
~/.config/taffybar: Remove superfluous spaces.
~/.vimrc: Add handy bindings for ternjs.vim.

Of these, `cw` is kind of troubling, because it also tries to "rename"
non-variables (e.g. in strings or comments).