Fix broken Cache-Control headers
Fix broken Cache-Control headers

The "public" or "private" keyword will be set by the stale? block and
merged with the remaining Cache-Control header.

We also cannot set no-cache, since it negates the meaning of private /
public and also causes rails to throw away everything else in the
Cache-Control header and just send "Cache-Control: no-cache".

Also always send max-age header, since max-age=0 is OK to indicate no
caching should be done.

ianheggie/health_check,ianheggie/health_check