0.0.3 - Better path handling, Rules return Tasks

A project looking to use Hancho needs more granular control of directories and paths. I've refactored the code so that there are now a number of predefined path variables that Rules can use to assemble "task_dir"/"in_dir"/"out_dir"/"deps_dir" as they like (documentation coming shortly).

Also, calling a Rule now returns a Task object instead of just a filename promise. This should make Rules that ingest Tasks more flexible.