Started work on Invariants and Zombies (issue #34)

  Just set up the structure, exted the biography and filled in the short description.
Included Biran Foote's famous "Big Ball of Mud" Paper in bibliography
Merge branch 'gernots' into instrumentation_and_invariants
Merge branch 'gernots' into instrumentation_and_invariants
Incorporate main line changes
added list-punctuation for assertions
New pattern: Use Invariants to Kill Zombies (issue #34)
  Completed work on this specific use of invariants
  Also added some bibliography along the way
  and corrected a small typo in the pattern index (missing dot before assertions)
Merge branch 'gernots' into invariants_and_zombies
Merge pull request #41 from MichaelMahlberg/invariants_and_zombies

Invariants and zombies, sounds good!