installation: improvement of OS X installation
installation: improvement of OS X installation

* Removes `sudo` command when installing bower, less ,
  clean-css, requirejs, uglify-js.

* Fixes some `note` elements.

Signed-off-by: Konstantinos Kostis <237b836d1007d10b89d97a8c1749c99bbd9efc26@cern.ch>

inveniosoftware/invenio,inveniosoftware/invenio,tiborsimko/invenio,tiborsimko/invenio