F2 version 1.3.1

On the heels of the release of version 1.3.0, we're tracking changes for version 1.3.1. [Review the milestone](https://github.com/OpenF2/F2/issues?milestone=16&state=open) for tracking Issues.

- [x] #108 (via #140)
- [x] Rewrite [readme](https://github.com/OpenF2/F2/blob/1.3.1-wip/README.md)
- [x] Rewrite [contribution guidelines](https://github.com/OpenF2/F2/blob/1.3.1-wip/CONTRIBUTING.md)
- [x] Add documentation for `AppConfig.enableBatchRequests`
- [x] Minor edits to Context: Container-to-App (Server) documentation
- [x] Added note to [docs](https://github.com/OpenF2/F2/blob/1.3.1-wip/docs/src/container-development.md#about-bootstrap-3) on continued usage of [TwBS 2.3.2](http://getbootstrap.com/2.3.2/) (F2 has not upgraded to v3)