CirlceCI: install plpythonu

Author: NikolayS

circle.yml

@@ -1,6 +1,9 @@
 machine:
     services:
         - postgresql
+dependencies:
+    post:
+        - sudo sudo apt-get update && sudo apt-get install postgresql-contrib-9.5
 database:
     override:
         - sudo -u postgres psql -c "create database test;"