Bump java buildpack

git shortlog c26eb3f..1e98b91
Glyn Normington (2):
      add invalid JDK example; ensure .jdk directory is cleaned up
      switch to RSpec 2 syntax

Jennifer Hickey (1):
      Upgrade to Tomcat 7

jencompgeek (1):
      Merge pull request #2 from glyn/test-invalid-jdk