community/libvterm: upgrade to 0.1.4

This had me confused for a bit, like, what is the right place to pull this from?

http://www.leonerd.org.uk/code/libvterm/ point to this empty folder http://bazaar.leonerd.org.uk/c/libvterm/ (the .bzr/ folder isn't listed by the web server).

Our previous upstream source has no releases but a 0.1.3 bump over a year ago https://github.com/neovim/libvterm/commits/nvim

There's no 0.1.4 download from here https://launchpad.net/libvterm/+download linked from here http://www.leonerd.org.uk/code/libvterm/libvterm-0.1.4.tar.gz

But Ubuntu and Debian seem to have packaged 0.1.4, as well as void-linux https://github.com/void-linux/void-packages/blob/master/srcpkgs/libvterm/template