Modified $database and "Etag" -> "ETag"

Using the keyword "static" for database would throw an error any time it was changed manually (i.e. there is no "set_database" function (nor is there any real need for one)). All instances of "Etag" were changed to "ETag" as the head request returns "ETag"s.
Merge pull request #2 from dpmooney/patch-2

Modified $database and "Etag" -> "ETag"