Merge pull request #1 from giokokos/feedback-btn

CSS styles for button
faster transitions of the modals

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>
redesign of feedback button

NOTE: uses font-awesome icon which is available only in the
      overlay

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>