Collect stderr from launcher when launching server

This makes it a LOT easier to debug things ;-)

The patch refactors how we read stdout a bit as well,
in two ways:
 - once we were reading stderr, I wanted to put the
   close() for out and err in the same spot otherwise
   it looked like a bug
 - handle URISyntaxException and keep going, don't only
   read the first line, per the TODO.
Merge pull request #118 from sbt/wip/havocp-show-launcher-errors

Collect stderr from launcher when launching server