Updated content in preparation for release.

* README
  * Added 'Downloads' section
  * Added contact blurb
  * Added/fixed links where appropriate
  * Fixed http/https access where appropriate
* Updated license year as it seems the license should always be
  copyright the current year, but I am not sure if that is correct or
  not.
* Added more explanation of directory structure to CONTENTS.md
* Updated contributors for 2013
* Updated development guide with current conventions