Server stops when reloader is triggered

[isbadawi]

This is not a bug per se, but it's annoying for development. Probably related to pymatbridge -- usually the server won't restart until a stray Matlab or Octave process is killed.

[isbadawi]

There's a few things going on here.

• The immediate problem is that when pymatbridge spawns the matlab/octave process, that process inherits the open files and ports, so when the reloaded process tried to bind to the port, it's still being used. The way to fix this is to pass close_fds=True to subprocess.Popen -- could probably send a PR to fix this.
• If we do this, then when the server reloads, it won't reuse the same matlab session, because pymatbridge starts up a server each time. Could maybe split off a separate connect() method for those cases when we know there's a server already running.