Add parallel_predict_traits.py
Improve memory usage when combining files

Simply code in parallel_predict_traits.py and more importantly
ensure only one of the output files is combined in memory at a single time.
Add delay option and speed up combine in parallel_predict_traits.py

Allow the user to add a delay (sleep) between each job submission in seconds.

Also, vastly speed up file combining by using += instead of = blah+blah
Merge pull request #132 from mlangill/parallelize_predict_traits

Add parallel_predict_traits.py