Allow hiverc to be a list so that multiple RC files can be loaded. The hive command hive
Updated the doc string of the hiverc function.
send outputs back into yield statement (for dynamic requirements, #424)
Merge pull request #464 from vishalrp/master

Allow multiple hiverc files.
Implement Task.previous and Task.get_previous_completed

Move from Spotify internal to public
Refactor previous as utility functions
Use clone instead of class constructor
Merge pull request #473 from spotify/erikbern/dynamic-reqs-fix

send outputs back into yield statement (for dynamic requirements, #424)
More tests for priority
Merge pull request #474 from spotify/erikbern/priority-doc

More tests for priority
Move previous to util.py
Merge pull request #472 from sisidra/sisidra/task-previous

Implement Task.previous and Task.get_previous_completed