pastebuf.lua 0.3: more paste sites, support unrecognized url, run cmd

- added paste.ee and paste.is (thanks to Gussi <gussi@gussi.is>)
- support url of hidden paste from paste.debian.net
- added option to allow opening urls from unsupported/unrecognized
  services
- added `run` command to be used inside paste buffer. with it you can
  pass the content of paste shown in current buffer to a shell command