better help for mail server option
Merge pull request #299 from Topface/mail-server-help

Better help for mail server option
Clear job graph when no longer leader.

When re-elected, Chronos attempts to re-create the job graph; this
patch prevents doing so with vertexes that are already in the job
graph, which is an illegal operation.
Merge pull request #300 from DevOps-TangoMe/master

Clear job graph when no longer leader.
Don't schedule queued jobs if they have been disabled
Remove a meaningless function invoking

Invoking skipForwad is not needed if job.schedule cannot be parsed.
So it is meaningless to parse it twice.
Merge pull request #303 from meelapshah/master

Don't schedule queued jobs if they have been disabled
Merge pull request #306 from depay/master

Remove a meaningless function invoking
Change type of disk and mem from int to double

Disk and mem in resources from Mesos are double but not integer.
Using integer may lead resouce in mesos becoming some number
like 1.0*e-15 instead of 0.
Merge pull request #308 from depay/master

Change type of disk and mem from int to double
Fix: task isn't removed from zk when failure hanppens

Persisting the old taskId but not the new one when handling failed task
causes the problem.
Merge pull request #309 from depay/master

Fix: task isn't removed from zk when failure hanppens