message: Update rust style guide
diff: @@ -69,7 +69,7 @@ described below, but even so, many portions of this guide will need to be
  handled manually.
  ### Line Width
  -Each line in the source file should be of a maximum of 80 characters of text.
  +Each line in the source file should be of a maximum of 100 characters of text.
  This includes comments.
  ### Imports
  @@ -398,12 +398,23 @@ where T: Printer {
  }
  ```
  +We also have a specific _ordering_ for `impl` definitions. It is as follows:
  +
  +1. The "main" `impl` for a type, containing its associated behaviour.
  +2. Getter implementations, if present.
  +3. Setter implementations, if present.
  +4. Trait implementations for the type, if present.
  +5. The "internal" `impl` block for that type, if present.
  +
  +Each of these should be accompanied by a sub-heading.
  +
  ### Getters and Setters
  We have the following rules for getters and setters in our codebase.
  - Getters do not have the `get_` prefix, while setters do have the `set_`
  prefix.
  -- If a setter is provided, a `mut` accessor should be provided as well.
  +- If a setter is provided, a `mut` accessor should be provided as well as part
  + of the setters `impl` block.
  Correct examples for the definition of getters and setters can be found below:
  @@ -421,6 +432,9 @@ fn set_field(&mut self, val:Type) {
  }
  ```
  +Getters and setters should be implemented in separate `impl`, blocks, each with
  +their own subheading.
  +
  ### Trait Exports
  All names should be designed to be used in a qualified fashion. This does,
  however, make one situation quite tricky. In order to use methods defined inside
  