Adding 'Executing the migrations' subsection into README.md. Adding log messages on deploy.yml.

README.md

@@ -59,6 +59,23 @@ In this command:
 - The **-dir** flag indicates that we want to store the migration files in the **./migrations** directory (which will be created automatically if it doesn't already exist).
 - The name **create_movies_table** is a descriptive label that we give the migration files to signify their contents.
 
+### Executing the migrations
+
+```bash
+migrate -path=./migrations -database=$GREENLIGHT_DB_DSN up
+```
+Note: You may get the error: **error: pq: permission denied for schema public...** when running this command. It's because Postgres might revoke the **CREATE** permission from all users except a database ownser. 
+
+To get around this, set the database owner to the **greenlight** user: 
+```sql
+ALTER DATABASE greenlight OWNER TO greelight;
+```
+
+If that still doesn't work, try explicitly granting the **CREATE** privileges to the **greenlight** user:
+```sql
+GRANT CREATE ON DATABASE greenlight TO greelight;
+```
+
 ## Additional Information
 
 ### How different Go Types are encoded