Update CONTRIBUTING.md

update CONTRIBUTING.md with more information

More information on how to contribute. This will necessitate a need to have branch(es) `release/x.x` live continuously. Bug fixes PR to `release/x.x` pushed to `master` and `develop` which is the same as having a `hotfix` branch which lives for a short time frame pushing at same branches. Once bug fixes are pushed into a `release` branch a new release is tagged and zipped. 

Features which do not break b/c can be pushed into the current `release` branch from `develop` then into `master`. Release can be issued by tagging and zipping the next release.