Tag 0.18.0 as version 0.18.0 [ci skip]

bin/version

 #!/usr/bin/env bash
 
-VERSION="v0.18.0-snapshot"
+VERSION="v0.18.0"
 
 # dynamically pull more interesting stuff from latest git commit
 HASH=$(git show-ref --head --hash=7 head)            # first 7 letters of hash should be enough; that's what GitHub uses