Make sure there actually is an object
Respect existing/concious Cache-Control headers

I realize this extension find it desirable to cache everything
for a week. But overriding existing Cache-Control headers will
introduce huge site compatibility issues. If the header exists,
someone somewhere must have taken a conscious decision about how
long the content can be cached. Or if it even can be cached.

Removing the override on existing headers will cause fewer
issues for end-users.
Faster object creation
Merge pull request #3 from Aeyoun/master

Compatibility improvements