Bugfix: X-Total-Entries on /observations was broken.

For some reason that wasn't working w/ @pleary's pagination count
optimization. Many thanks to him for finding this solution.
Merge pull request #285 from pleary/paths

Fixed extensions in atom and kml links; added atom mime type; caught format error
Minor style change for messages.
Reverting cache change, since it introduces deeper bugs w/ bbox queries.