Sprintf() called w/o interface{} args

The original call will result in "/_cluster/health/%!s(MISSING)"

See: http://play.golang.org/p/PaKn5IjFl1

Presumably this was meant to be "/_cluster/health" with no additional arguments?
Merge pull request #83 from philhofer/patch-1

Sprintf() called w/o interface{} args