nginx: no caching for `/showcase` endpoint
nginx: no caching for `/showcase` endpoint

* Takes `/showcase` endpoint out of the nginx reverse proxy caching
  process, because this page needs server-side mobile browser
  detection. (closes #23)

Signed-off-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

tiborsimko/inveniosoftware.org