Add an example to the readme

README.md

@@ -4,3 +4,53 @@ multistep is a Go library for building up complex actions using discrete,
 individual "steps." These steps are strung together and run in sequence
 to achieve a more complex goal. The runner handles cleanup, cancelling, etc.
 if necessary.
+
+## Basic Example
+
+```go
+type stepAdd struct{}
+
+func (s *stepAdd) Run(state map[string]interface{}) multistep.StepAction {
+    // Read our value and assert that it is they type we want
+    value := state["value"].(int)
+
+    fmt.Printf("Value is %d\n", value)
+
+    state["value"] = value + 1
+
+    return multistep.ActionContinue
+}
+
+func (s *stepAdd) Cleanup(map[string]interface{}) {}
+```
+
+Call your step from a runner.
+
+```go
+func main() {
+    // Our "bag of state" that we read the value from
+    state := make(map[string]interface{})
+
+    // Our intial value
+    state["value"] = 0
+
+    steps := []multistep.Step{
+        &stepAdd{},
+        &stepAdd{},
+        &stepAdd{},
+    }
+
+    runner := &multistep.BasicRunner{Steps: steps}
+
+    // Executes the steps
+    runner.Run(state)
+}
+```
+
+This will produce:
+
+```
+Value is 1
+Value is 2
+Value is 3
+```