Upgrade Clustertools (#255)

Author: georgwiese

poetry.lock

@@ -12,7 +12,7 @@ numpy = "^1.17.4"
 pillow = "^6.2.1"
 wkw = "0.1.4"
 requests = "^2.22.0"
-cluster_tools = "1.50"
+cluster_tools = "1.51"
 natsort = "^6.2.0"
 psutil = "^5.6.7"
 nibabel = "^2.5.1"