Begin 2.5 changelog.

@shelob9 I got roughly to Nov 29, 2014
Finished changelog updates in readme.txt
Increase WordPress required version to 3.8
Update contributors in readme.txt #2499
Fix tip and missing period in changelog
Update changelog.
set release date
up stable tag
Add to changelog about additional nonces
Test #s
update notice
Readme updates for changelog and contributors list for Pods 2.5
Merge branch '2.x' into feature/2499

Conflicts:
	readme.txt
Merge pull request #2551 from pods-framework/feature/2499

Changelog update for 2.5