v3.0-rc10

Changed rc10:

• Fix: common snapshot could get deleted. (this happend due to a recent change in zfs-autobackup)
• Also thin out target-datasets that dont exist on the source anymore.
• Fix: Return correct error code, indicating the number of failed datasets.
• Fix: Flush all outputs to make sure stdout and stderr are synced.
• Automaticly enable --progress if output is a TTY.

Recent changes:

• exposed --min-change value as a parameter. (was hardcoded at 200000)
• Issue #25, disable colors on non-tty
• added --no-send option. snapshots that are obsolete are now destroyed at the beginning of each dataset-transfer. this allows using --no-send as way to just thinout old snapshots. cleaned up stderr output when resuming.
• Added support for custom ssh client config
• Improved --rollback and incompatible snapshot detection. added --destroy-incompatible.
• --min-change is now has 1 instead of 200000 as default. fixes #37
• added thinner documentation and cleared up thinner output texts.