Add more information from the Spring Framework document on maintaining a linear history as well as some code-style information
Copied from the Contributor Guidelines wiki document [1] in order to take advantage of GitHub's new integrated support for displaying a link to contributor guidelines when issuing a pull request [2]. [1]: https://github.com/SpringSource/spring-integration/wiki/Contributor-Guidelines [2]: https://github.com/blog/1184-contributing-guidelines For reference see: https://jira.springsource.org/browse/INT-2753