message: Note clang-format in CONTRIBUTING.md
diff: @@ -128,3 +128,13 @@ class foo {
  ### Relational Operators
  - Prefer to use free functions
  +
  +### Formatting
  +
  +The source includes a clang format definitions file (`.clang-format`) to enforce consistent style. Run clang-format (using 3.8) from the root of the repository or use the helper script included in the source:
  +
  +```
  +python ./etc/clang-format.py format
  +```
  +
  +Note, this script will automatically download clang-format 3.8 if it cannot detect it on your system.
  