Add stylesheet

  I have haven't studied ROR long time,  I gone my hometown  at May 1 and back I have a 
many annoying work item. finally, I extrude some time go on study.

  This times I add some simple stylesheet for event show page. I just reference "git issue pages" style. but, unlike. so I think I still have many content of CSS&HTML wait me learning.

  Peter, program have a bug, can you help modify that, witch is when user add content of comment is too long, and display will be super unsightly.