Fix issue related to command output filling up the IO pipe.

If command being run had output of more than 64k,the pipe would fill and
the process would hang waiting for room to write more data into the pipe.
Reading the pipe synchrously eliminates the problem.
See the following link for more detail on the problem and another solution.
http://stackoverflow.com/questions/13829830/ruby-process-spawn-stdout-pipe-buffer-size-limit/13846146#13846146