added tips postgres

HACKING.md

@@ -49,6 +49,16 @@
 
         GRANT ALL PRIVILEGES ON DATABASE namebase TO username;
 
+## Tips of Postgres
+
+1. List database
+
+        psql -l
+
+2. Delete database
+
+        dropdb namebase
+
 ## Conecting to Postgres
 
 1. Copy `settings.py.example` to `settings.py` and modify.