Add realtime output from solver

Hey, great job with this ampl magic for ipython, found it super useful in debugging models/visualizing solutions quickly without having to parse a solution file or use AMPL shell.
I made a small (and ugly) change to get realtime output from the solver showing up inline, not only when the optimization is over, don't know if you like . (Probably should have just filed an issue instead of a pull request? Github noob here.)
By the way, there's an issue when stopping the execution in IPython notebook. 
In a (ipython) shell, Ctrl+C stops AMPL *and* solver, but in the notebook the solver is left hanging - and keeps eating CPU unless I kill it, or wait for the optimization to end.