Merge pull request #154 from dgraph-io/rahulgurnani/docs

docs: Add information about whitelist IPs

Author: rahulgurnani

examples/simple/README.md

@@ -24,8 +24,9 @@ services:
       - 8080:8080
       - 9080:9080
     restart: on-failure
-    command: dgraph alpha --my=server:7080 --lru_mb=2048 --zero=zero:5080
+    command: dgraph alpha --my=server:7080 --lru_mb=2048 --zero=zero:5080 --whitelist "${WHITELISTED}"
 ```
+The "WHITELISTED" environment variable can be intiialized as described [in this post](https://discuss.dgraph.io/t/suggestion-for-how-to-add-docker-compose-network-to-whitelist/9600). We need to whitelist these IPs because the docker container runs with it's own IP address.
 
 ## Install the Dependencies