IPython loading speedups

1) Swapped IPython to use the piping style loading, which is significantly faster.
2) Refactored the loading step a little bit to remove some unused functions.
3) Cluster startup refactored: Only spin up one cluster, then pass a view to it, to save on the cluster startup time for a busy scheduler.
4) Added Torque support and removed generic PBS support.

This closes https://github.com/arq5x/gemini/issues/84 and https://github.com/arq5x/gemini/issues/83.