'reactivemanifesto' ribbon has size issues on mobile browsers

[strobe]

For instance if you tried to read Play documentation on the phone the ribbon will be shield big portion of useful text - I guess that this ribbon should very tiny on small screen sizes.

tested on: ios 7 - safari, chrome ; android 4.0.4 chrome

[rasummer]

@strobe Going to add an issue to the Playframework repo to address this.