Merge pull request #9936 from bljordan/bjordan/spot_datafeed_subscription_docs

Update documentation for aws_spot_datafeed_subscription.

website/source/docs/providers/aws/r/spot_datafeed_subscription.html.markdown

@@ -22,12 +22,13 @@ resource "aws_s3_bucket" "default" {
 
 resource "aws_spot_datafeed_subscription" "default" {
 	bucket = "${aws_s3_bucket.default.bucket}"
+	prefix = "my_subdirectory"
 }
 ```
 
 ## Argument Reference
 * `bucket` - (Required) The Amazon S3 bucket in which to store the Spot instance data feed.
-* `prefix` - (Optional) A prefix for the data feed file names.
+* `prefix` - (Optional) Path of folder inside bucket to place spot pricing data.
 
 
 ## Import
@@ -36,4 +37,4 @@ A Spot Datafeed Subscription can be imported using the word `spot-datafeed-subsc
 
 ```
 $ terraform import aws_spot_datafeed_subscription.mysubscription spot-datafeed-subscription
-```
+```