Toil

This release contains critical bugs (1005 and 1007) and should not be used.

- Fix: User scripts fail when installed in a virtualenv that was created with --system-site-packages (929)
- Fix: Job functions fail to load if they are spread across more than one module (930, 831)

Changes:
- Fix rare bugs in Mesos scheduler (674, 672)
- Fix occasionalNoSuchJobException during --restart (639)

Changes
- Fix: Occasional KeyError during --restart (582, Christopher "CJ" Ketchum)
- Fix: Chained jobs overwrite each other's statistics with --stats (624, Christopher "CJ" Ketchum)
- Improve performance of --restart (Adam Novak)
- Fix: Mesos batch system doesn't favor bigger tasks (624, Hannes Schmidt)
- Various CWL integration fixes (Peter Amstutz, Kyle Elrott)
- Fix: Permission denied when adding files to job store that are not owned by current user (Adam Novak)