Fix run with .meteor/release lacking METEOR@

Otherwise:

  $ meteor
  meteor
  [[[[[ /private/tmp/p107 ]]]]]

  => Started proxy.
  => Started MongoDB.
  => Started your app.

  => App running at: http://localhost:3000/
  Your app has been updated to Meteor 1.0-rc.7 from Meteor 1.0-rc.7.
  Restart meteor to use the new release.