message: Add information on including atoms
diff: @@ -33,6 +33,7 @@ is a useful way of thinking about things when discussing type signatures.
  - [Behaviour of Type Signatures](#behaviour-of-type-signatures)
  - [Operations on Types](#operations-on-types)
  - [Type Definitions](#type-definitions)
  + - [Body Atom Definitions](#body-atom-definitions)
  - [Visibility and Access Modifiers](#visibility-and-access-modifiers)
  <!-- /MarkdownTOC -->
  @@ -322,6 +323,28 @@ type Monoid
  use Nothing
  ```
  +### Body Atom Definitions
  +
  +When defining an atom in the body of a type (as described above), there are two
  +ways in which you can define an atom:
  +
  +1. **Create a New Atom:** Using the `type` keyword inside the body of a type
  + will define a _new_ atom with the fields you specify. The syntax for doing
  + this is the same as that of a bare atom.
  +
  +```ruby
  +type Just value
  +```
  +
  +2. **Include an Atom:** You can also use a type body to define methods on an
  + already existing atom. To do this, you can _include_ the atom in the type's
  + body by naming it explicitly. This will introduce it into the scope of your
  + type and define any methods you define in your type on the included atom.
  +
  +```ruby
  +Nothing
  +```
  +
  ### Visibility and Access Modifiers
  While we don't usually like making things private in a programming language, it
  