Port fix for Update how certain cache directives are handled to 1.0.x

[JunTaoLuo]

The fix for #83 needs to go into LTS 1.0.x branch.

[JunTaoLuo]

Need to discuss which parts of the fixes in #88 needs to be back ported to 1.0.x

At the minimum, we'll need the fix for using If-Modified-Since instead of the incorrect If-Unmodified-Since.

We can potentially also add the handling of proxy-revalidate, and max-stale with no specified limit since those are low risk but they are not critical. May also consider porting the fix for #81 for consistency but it's not used by MVC since the ResponseCacheAttribute is a 1.1 feature.

[JunTaoLuo]

cc @muratg

[muratg]

(Setting milestone to 1.0.1 to reflect the actual package version to be shipped.)