update documentation

README.md

@@ -36,7 +36,7 @@ func (g generic) Run(job hive.Job, ctx *hive.Ctx) (interface{}, error) {
 
 // OnChange is called when Hive starts or stops a worker to handle jobs,
 // and allows the Runnable to set up before receiving jobs or tear down if needed.
-func (g generic) OnChange(change ChangeEvent) error {
+func (g generic) OnChange(change hive.ChangeEvent) error {
 	return nil
 }
 ```

docs/getstarted.md

@@ -21,7 +21,7 @@ func (r recursive) Run(job hive.Job, ctx *hive.Ctx) (interface{}, error) {
 	return fmt.Sprintf("finished %s", job.String()), nil
 }
 
-func (r recursive) OnChange(change ChangeEvent) error {
+func (r recursive) OnChange(change hive.ChangeEvent) error {
 	return nil
 }
 ```
@@ -129,6 +129,12 @@ doBad := h.Handle("badRunner", badRunner{}, hive.RetrySeconds(1), hive.MaxRetrie
 ```
 Any error from a failed worker will be returned to the first job that is attempted for that Runnable.
 
+### Pre-warming
+When a Runnable is mounted, it is simply registered as available to receive work. The Runnable is not actually invoked until the first job of the given type is received. For basic Runnables, this is normally fine, but for Runnables who use the `OnChange` method to provision resources, this can cause the first job to be slow. The `PreWarm` option is available to allow Runnables to be started as soon as they are mounted, rather than waiting for the first job. This mitigates cold-starts when anything expensive is needed at startup.
+```
+doExpensive := h.Handle("expensive", expensiveRunnable{}, hive.PreWarm())
+```
+
 ### Shortcuts
 
 There are also some shortcuts to make working with Hive a bit easier: