Added flush option for dataloader to doc.

Author: Simon Prickett

README.md

@@ -24,7 +24,7 @@ How to Start the RediSolar Application
 ### When using Redis on localhost, port 6379 with no password:
 
 1. Run `mvn package` to build your application.
-2. Load the sample data: `java -jar target/redisolar-1.0.jar load`.
+2. Load the sample data: `java -jar target/redisolar-1.0.jar load`.  If you want to erase everything in Redis before loading the data, use `java -jar target/redisolar-1.0.jar load --flush true`, but be aware that this will delete ALL keys in your Redis database.
 3. To check that your application is running enter url `http://localhost:8081`, substituting `localhost` for the hostname that you're running the application on if necessary.
 
 ### When using Redis on another host, port or with a password: