Handle process I/O correctly

[ndw]

There's a bug in the way that p:exec uses the Process object. I'm just assuming that I can write all of the output (the input to the process) before I read the input (the output from the process). But if the output is large enough, and the process begins writing its output before I finish writing its input, then we can get into a deadlock situation where the process can't continue because it's waiting for someone to read its output and I never get there because I'm stuck waiting to write its input.

[ndw]

This is fixed in 1.3.0