The document recommends a non-durable location for data

I noticed the documentation recommends a non-durable local resource for the Elasticsearch data path.  Although this is acceptable for some deployments it might be worth warning people that the path is not durable and there is a potential for data loss, even with replicas data loss is theoretically possible.

```
# recommended
path.data: /mnt/resource/elasticsearch/data
```

Alternatively the user could attach and use data disks which do come with a significant performance tradeoff, but premium storage options with higher IOPS have been announced and are right around the corner.

Closes #46.

Author: dadoonet

README.md

@@ -45,9 +45,6 @@ cloud:
         service_name: your_azure_cloud_service_name
 discovery:
         type: azure
-
-# recommended
-# path.data: /mnt/resource/elasticsearch/data
 ```
 
 How to start (short story)
@@ -294,8 +291,8 @@ cloud:
 discovery:
         type: azure
 
-# Recommended
-path.data: /mnt/resource/elasticsearch/data
+# Recommended (warning: non durable disk)
+# path.data: /mnt/resource/elasticsearch/data
 ```
 
 Restart elasticsearch: