Add usage instructions to README

Author: adammck

README.md

@@ -1,12 +1,31 @@
 # Terraformed Inventory
 
-This is a little Go app which generates an [Ansible] [ansible] inventory file
-from a [Terraform] [tf] state file.
+This is a little Go app which generates an dynamic [Ansible] [ansible] inventory
+from a [Terraform] [tf] state file. It allows one to spawn a bunch of VMs with
+Terraform, then (re-)provision them with Ansible. It's pretty neat.
+
+
+## Usage
+
+Just download the OSX binary and run it.
+
+    curl https://github.com/adammck/terraformedinventory/releases/download/v0.1/terraformedinventory
+    ./terraformedinventory --list whatever.tfstate
+
+Ansible doesn't (seem to) support calling the inventory script with parameters,
+so I like to wrap this tool up in a little shell script, and call that.
+Something like:
+
+	#!/bin/bash
+	terraformedinventory $@ $(dirname $0)/deploy/terraform.tfstate
+
+Configuration via environment variables, like most other dynamic inventory
+scripts, is coming soon.
 
 
 ## Development
 
-[Install Terraform] [tfdev], then:
+[Install Terraform] [tfdev] from source, then:
 
 	git clone https://github.com/adammck/terraformedinventory.git
 	cd terraformedinventory