Improve output cache.
Merge branch 'develop' of https://github.com/EllisLab/CodeIgniter into feature/output-cache-improvements
Merge branch 'develop' of https://github.com/EllisLab/CodeIgniter into feature/output-cache-improvements
Return spacing on var definitions.

Signed-off-by: Eric Roberts <eric@cryode.com>
Merge pull request #2151 from cryode/feature/output-cache-improvements

Add headers to Output class cache files.