Add docs and warning

Add web documentation, and include a warning about the conflict between
aws_elb_attachment and aws_elb.instances.

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

@@ -10,6 +10,12 @@ description: |-
 
 Provides an Elastic Load Balancer resource.
 
+~> **NOTE on ELB Instances and ELB Attachments:** Terraform currently
+provides both a standalone [ELB Attachment resource](elb_attachment.html)
+(describing the instances attached to an ELB), and an ELB resource with
+`instances` defined in-line. At this time you cannot use an ELB with in-line
+instaces in conjunction with an ELB Attachment resource. Doing so will cause a
+conflict of rule settings and will overwrite rules.
 ## Example Usage
 
 ```

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

@@ -0,0 +1,34 @@
+---
+layout: "aws"
+page_title: "AWS: aws_elb_attachment"
+sidebar_current: "docs-aws-resource-elb-attachment"
+description: |-
+  Provides an Elastic Load Balancer Attachment resource.
+---
+
+# aws\_elb\_attachment
+
+Provides an Elastic Load Balancer Attachment resource.
+
+~> **NOTE on ELB Instances and ELB Attachments:** Terraform currently provides
+both a standalone ELB Attachment resource (describing the instances attached to
+an ELB), and an [Elastic Load Balancer resource)[elb.html] with
+`instances` defined in-line. At this time you cannot use an ELB with in-line
+instaces in conjunction with an ELB Attachment resource. Doing so will cause a
+conflict of rule settings and will overwrite rules.
+## Example Usage
+
+```
+# Create a new load balancer attachment
+resource "aws_elb_attachment" "baz" {
+  elb      = "${aws_elb.bar.id}"
+  instances = ["${aws_instance.foo.id}"]
+}
+```
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `elb` - (Required) The name of the ELB.
+* `instances` - (Required) A list of instance ids to place in the ELB pool.