Fixed broken link to plugin.md to weave-docker-api.md.

site/weave-docker-api.md

@@ -28,7 +28,7 @@ Docker containers are started with the --net flag, for example:
 
 Note that if a Docker container is started with the --net flag, then the Weave Docker API Proxy
 is automatically disabled and is not used to attach containers. 
-See [Integrating Docker via the Network Plugin](plugin.md).
+See [Integrating Docker via the Network Plugin](/site/plugin.md).
 
 **3.** Containers can also be attached to the Weave network with `weave run` commands. This method also
 does not use the Weave Docker API Proxy.