doc: updated documentation related to node specific arguments

Author: satra

CHANGES

@@ -1,7 +1,7 @@
 Changes since 0.5
 =================
 
-None
+* API: Node now allows specifying node level configuration for SGE/PBS clusters
 
 Release 0.5 (Mar 10, 2012)
 ==========================

doc/users/plugins.rst

@@ -115,6 +115,22 @@ a custom template::
        workflow.run(plugin='SGE',
           plugin_args=dict(template='mytemplate.sh', qsub_args='-q myqueue')
 
+In addition to overall workflow configuration, you can use node level
+configuration for PBS/SGE::
+
+    node.plugin_args = {'qsub_args': '-l nodes=1:ppn=3'}
+
+this would apply only to the node and is useful in situations, where a
+particular node might use more resources than other nodes in a workflow.
+
+.. note::
+
+  Setting the keyword `overwrite` would overwrite any global configuration with
+  this local configuration::
+
+     node.plugin_args = {'qsub_args': '-l nodes=1:ppn=3', 'overwrite': True}
+
+
 Condor
 ------