test(travis): fixing travis config to use firefox

Author: ocombe

.travis.yml

@@ -16,3 +16,6 @@ after_success:
 branches:
   except:
     - "/^v\\d+\\.\\d+\\.\\d+$/"
+before_script:
+  - export DISPLAY=:99.0
+  - sh -e /etc/init.d/xvfb start

karma.conf.js

@@ -75,7 +75,7 @@ module.exports = function(config) {
         singleRun: true,
 
         // Concurrency level
-        // how many browser should be started simultanous
+        // how many browser should be started simultaneous
         concurrency: Infinity
     })
 };