#61 Suggestions for improvement of developers guide

[Kai Hartmann]

Just a few points:

• add @cdk.XXX tag documentation to "Doc" section
• make a list of possible junit test targets
  (assertTrue, assertEquals, assertWhatever)
• CDK modules - mention which dependencies they have
  (io depends on core, ...)
• change release manager to current person
• things to remember before commit (update, test,
  CHANGELOG)

All-in-all a quite comprehensive guide on a few pages.
Please keep it that way. Good work.