Added information relevant to the github transition in RELEASE_NOTES.md,
transition document.

Remoted plain text release_notes moving forward.  Created a markdown
version of the README file as an experiment to see what we think. 
GitHub will render markdown natively, as does Doxygen and our new
build system.
Delete README-SVN-TRANSITION-TO-GITHUB.txt

File will live in the subversion repository as a breadcrumb trail to GitHub; it does not need to exist here.
Merge branch 'master' into ward-dev

* master:
  Delete README-SVN-TRANSITION-TO-GITHUB.txt
  Added information relevant to the github transition in RELEASE_NOTES.md, transition document.