message: doc(contributing): Add section about binary diffs
  This adds instructions on how to set up human-readable binary diffs
  with git for Etcher, which is useful when altering test images etc.
diff: @@ -69,6 +69,28 @@ systems as they can before sending a pull request.
  *The test suite is run automatically by CI servers when you send a pull
  request.*
  +Diffing Binaries
  +----------------
  +
  +Binary files are tagged as "binary" in the `.gitattributes` file, but also have
  +a `diff=hex` tag, which allows you to see hexdump-style diffs for binaries,
  +if you add the following to either your global or repository-local git config:
  +
  +```sh
  +$ git config diff.hex.textconv hexdump
  +$ git config diff.hex.binary true
  +```
  +
  +And global, respectively:
  +
  +```sh
  +$ git config --global diff.hex.textconv hexdump
  +$ git config --global diff.hex.binary true
  +```
  +
  +If you don't have `hexdump` available on your platform,
  +you can try [hxd], which is also a bit faster.
  +
  Sending a pull request
  ----------------------
  @@ -108,3 +130,4 @@ Don't hesitate to get in touch if you have any questions or need any help!
  [RUNNING-LOCALLY]: https://github.com/resin-io/etcher/blob/master/docs/RUNNING-LOCALLY.md
  [EditorConfig]: http://editorconfig.org
  [shrinkwrap]: https://docs.npmjs.com/cli/shrinkwrap
  +[hxd]: https://github.com/jhermsmeier/hxd
  