Moving to a 3 month release cycle

[Owen O'Malley]

As the users of Hadoop ask for more stability and fewer release  
upgrades to deal with, I think we should move the release cycle out  
to 3 months from the current 2. I propose that we move the feature- 
freeze date for 0.16 to the first week of January and 0.17 to first  
week of April.

Thoughts?
-- Owen