Implements #46: Hooks to run container launch / shutdown tasks.

Launch arbitrary user-specified executables on the host system
when containers are launched or destroyed. Environment
variables are passed to executable. Arguments may be specified
in deimos.cfg. Please see example.cfg.
Fix whitespace for PEP-8; Fix override method for Hooks class
Remove NODE_INFO example from example.cfg (since that's only for our environment)
Remove backslash line continuation as requested
Merge pull request #52 from sethdmoore/feature/docker-launch-destroy-command-hooks

Implements #46: Hooks to run container launch / shutdown tasks.