Fix client on Firefox 34.0 beta

Our ajax function was passing params as object to xhr.send function.
For some reason this breaks on Firefox 34.0 beta. Sending stringified
version of params works correctly.

assets/scripts/lib/travis/ajax.coffee

@@ -27,6 +27,9 @@ Travis.ajax = Em.Object.create
     !publicEndpoint || privateEndpoint
 
   ajax: (url, method, options) ->
+    # TODO: we have our own ajax implementation, because jQuery didn't
+    #       properly worked with headers on firefox, it would be nice to check
+    #       if this is still a problem and if we can remove this
     method = method || "GET"
     method = method.toUpperCase()
 
@@ -135,6 +138,10 @@ Travis.ajax = Em.Object.create
           reject(xhr)
           options.error.call(data, xhr.status, xhr)
 
-    xhr.send(options.data)
+    data = options.data
+    if typeof(options.data) == "object" && (Ember.isNone(options.contentType) || options.contentType.match /application\/json/)
+      data = JSON.stringify(data)
+
+    xhr.send(data)
 
     return promise