Drop support for IE9 and IE10 in dummy app

tests/dummy/config/targets.js

@@ -1,10 +1,19 @@
 /* eslint-env node */
+'use strict';
+
+const browsers = [
+  'last 1 Chrome versions',
+  'last 1 Firefox versions',
+  'last 1 Safari versions'
+];
+
+const isCI = !!process.env.CI;
+const isProduction = process.env.EMBER_ENV === 'production';
+
+if (isCI || isProduction) {
+  browsers.push('ie 11');
+}
 
 module.exports = {
-  browsers: [
-    'ie 9',
-    'last 1 Chrome versions',
-    'last 1 Firefox versions',
-    'last 1 Safari versions'
-  ]
+  browsers
 };