message: Fix README wording
  Touching up some fallout from
diff: -# Fathom (placeholder name)
  +# Fathom
  A declarative data definition language for formally specifying binary
  data formats.
  @@ -14,6 +14,6 @@ The work-in-progress language documentation can be found under the [docs directo
  ## License
  -The language is licensed under the terms of the Apache License (Version 2.0).
  +Fathom is licensed under the terms of the Apache License (Version 2.0).
  See [LICENSE](./LICENSE) or http://www.apache.org/licenses/LICENSE-2.0 for details.
  