executor: preserve RegExps in middleware paths

Fix interpolateVariables() to skip objects with a non-default
constructor, for example RegExp or Date.

lib/executor.js

@@ -354,6 +354,10 @@ function getUpdatedConfigObject(app, config) {
     if (Array.isArray(config))
       return config.map(interpolateVariables);
 
+    // Not a plain object. Examples: RegExp, Date,
+    if (!config.constructor || config.constructor !== Object)
+      return config;
+
     // recurse into object props
     var interpolated = {};
     Object.keys(config).forEach(function(configKey) {

test/executor.test.js

@@ -531,6 +531,19 @@ describe('executor', function() {
           done();
         });
     });
+
+    it('should preserve object prototypes', function(done) {
+      var config = simpleMiddlewareConfig(
+        'routes',
+        // IMPORTANT we need more than one item to trigger the original issue
+        [/^\/foobar/, /^\/another/],
+        {});
+      boot.execute(app, config);
+
+      supertest(app).get('/foobar')
+        .expect(200)
+        .end(done);
+    });
   });
 
   describe('with component-config.json', function() {
@@ -775,17 +788,26 @@ describe('executor', function() {
 
 });
 
-function simpleMiddlewareConfig(phase, params) {
+function simpleMiddlewareConfig(phase, paths, params) {
+  if (params === undefined) {
+    params = paths;
+    paths = undefined;
+  }
+
+  var config = {
+    phase: phase,
+    params: params
+  };
+
+  if (paths) config.paths = paths;
+
   return someInstructions({
     middleware: {
       phases: [phase],
       middleware: [
         {
           sourceFile: path.join(__dirname, './fixtures/simple-middleware.js'),
-          config: {
+          config: config,
-            phase: phase,
-            params: params
-          }
         }
       ]
     }