function runEnterHooks(routes, nextState, callback) {
	  var hooks = getEnterHooks(routes);
	  return runTransitionHooks(hooks.length, function (index, replace, next) {
	    hooks[index](nextState, replace, next);
	  }, callback);
	}
Runs all onEnter hooks in the given array of routes in order
with onEnter(nextState, replace, callback) and calls
callback(error, redirectInfo) when finished. The first hook
to use replace short-circuits the loop.

If a hook needs to run asynchronously, it may use the callback
function. However, doing so will cause the transition to pause,
which could lead to a non-responsive UI if the hook is slow.