Use XMLHttpRequest directly

jQuery uses getAllResponseHeaders function for getting response headers,
even for getResponseHeader. As far as I know, there is no easy way to
get original xhr object and call getResponseHeader on such object.
Because of that getResponseHeader is broken on firefox with CORS.

I rewrote Travis.ajax to use XMLHttpRequest directly in order to fix
this, the compatibility with jQuery.ajax is mostly handled.
No need to do hacks with Location header or Content-Type anymore
Use $.ajax when testing to not break jquery.mockjax
Use view.jobIdForLog instead of showDownloadLog

The latter is not always refreshed, I don't have time to debug it more
thoroughly
Update Ember.js
Router changes for new ember.js
sign out before resetting app
Use jQuery.param for generating query string