throw a TypeError on non-function handler closes #31

Author: jonathanong

index.js

@@ -24,6 +24,10 @@ function create(method) {
     const re = pathToRegexp(path, keys, opts);
     debug('%s %s -> %s', method || 'ALL', path, re);
 
+    if (typeof fn !== 'function') {
+      throw new TypeError('Route handler must be a function');
+    }
+
     const createRoute = function(routeFunc) {
       return function (ctx, next){
         // method