- not the current Cbc builds

- copied from Ipopt 3.13 Changelog

- remove GAMS from list of binaries: it contains a Cbc library, but that
  is only usable via GAMS; thus having GAMS in the list of interfaces
  should be sufficient

- nodelimit did not change, just solution limit, and that's of little interest

- converted docbook to markdown
- source now in gh-pages branch, so remove Cbc/doc
- some cleanup
- update link in README.md

- integrate some content from Cbc trac wiki start page