Merge pull request kubernetes#571 from alpe/flex_doc

Fix example flex driver links in flexvolume document

contributors/devel/flexvolume.md

@@ -89,7 +89,7 @@ Unmount the volume. This call-out defaults to bind mount for drivers which imple
 <driver executable> unmount <mount dir>
 ```
 
-See [lvm](lvm) & [nfs](nfs) for a quick example on how to write a simple flexvolume driver.
+See [lvm] & [nfs] for a quick example on how to write a simple flexvolume driver.
 
 ### Driver output:
 
@@ -121,8 +121,13 @@ Note: Secrets are passed only to "mount/unmount" call-outs.
 
 ### Example of Flexvolume
 
-See [nginx.yaml](https://github.com/kubernetes/kubernetes/blob/master/examples/volumes/flexvolume/nginx.yaml) & [nginx-nfs.yaml](https://github.com/kubernetes/kubernetes/blob/master/examples/volumes/flexvolume/nginx-nfs.yaml) for a quick example on how to use Flexvolume in a pod.
+See [nginx.yaml] & [nginx-nfs.yaml] for a quick example on how to use Flexvolume in a pod.
 
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+
+[lvm]: https://github.com/kubernetes/kubernetes/blob/master/examples/volumes/flexvolume/lvm
+[nfs]: https://github.com/kubernetes/kubernetes/blob/master/examples/volumes/flexvolume/nfs
+[nginx.yaml]: https://github.com/kubernetes/kubernetes/blob/master/examples/volumes/flexvolume/nginx.yaml
+[nginx-nfs.yaml]: https://github.com/kubernetes/kubernetes/blob/master/examples/volumes/flexvolume/nginx-nfs.yaml