Add saucelabs browser testing to travis

package.json

@@ -19,6 +19,7 @@
     "karma-jasmine": "^1.1.1",
     "karma-chrome-launcher": "^2.2.0",
     "karma-firefox-launcher": "^1.1.0",
+    "karma-sauce-launcher": "^1.2.0",
     "karma-webpack": "^2.0.9",
     "karma-sourcemap-loader": "^0.3.7",
     "ts-loader": "^3.3.1"
@@ -26,7 +27,7 @@
   "scripts": {
     "test": "gulp test",
     "lint": "gulp lint",
-    "browser-test": "karma start --single-run"
+    "browser-test": "karma start"
   },
   "repository": {
     "type": "git",