refine and refactor signup test and implementation

Changes:

1bff5ac (Charles A. Beynon, 30 minutes ago)
   refactor flash divs in application layout

f7122af (Charles A. Beynon, 33 minutes ago)
   test signup success page for title and flash message

ea8a4c3 (Charles A. Beynon, 43 minutes ago)
   refine tests for gravatar_for

db471ca (Charles A. Beynon, 9 hours ago)
   add optional size paramter to gravatar_for