merge.py usage message improvement
merge.py usage message improvement

http://codereview.appspot.com/2587


avilaton/transitfeed,zarnold/transitfeed,Censio/transitfeed,avilaton/transitfeed,Censio/transitfeed,galvinford/transitfeed,zarnold/transitfeed,bileto/transitfeed,digideskio/transitfeed,bileto/transitfeed,Censio/transitfeed,google/transitfeed,bileto/transitfeed,zarnold/transitfeed,digideskio/transitfeed,galvinford/transitfeed,google/transitfeed,google/transitfeed,avilaton/transitfeed,digideskio/transitfeed,galvinford/transitfeed