minor tweak to usage README.

Author: mattpolzin

documentation/usage.md

@@ -7,37 +7,37 @@ In this documentation, in order to draw attention to the difference between the
 
 - [`JSONAPI.ResourceObjectDescription`](#jsonapiresourceobjectdescription)
 - [`JSONAPI.ResourceObject`](#jsonapiresourceobject)
-	- [`Meta`](#meta)
-	- [`Links`](#links)
-	- [`MaybeRawId`](#mayberawid)
-		- [`RawIdType`](#rawidtype)
-	- [Convenient `typealiases`](#convenient-typealiases)
+    - [`Meta`](#meta)
+    - [`Links`](#links)
+    - [`MaybeRawId`](#mayberawid)
+        - [`RawIdType`](#rawidtype)
+    - [Convenient `typealiases`](#convenient-typealiases)
 - [`JSONAPI.Relationships`](#jsonapirelationships)
 - [`JSONAPI.Attributes`](#jsonapiattributes)
-	- [`Transformer`](#transformer)
-	- [`Validator`](#validator)
-	- [Computed `Attribute`](#computed-attribute)
+    - [`Transformer`](#transformer)
+    - [`Validator`](#validator)
+    - [Computed `Attribute`](#computed-attribute)
 - [Copying/Mutating `ResourceObjects`](#copyingmutating-resourceobjects)
 - [`JSONAPI.Document`](#jsonapidocument)
-	- [`ResourceBody`](#resourcebody)
-		- [nullable `PrimaryResource`](#nullable-primaryresource)
-	- [`MetaType`](#metatype)
-	- [`LinksType`](#linkstype)
-	- [`IncludeType`](#includetype)
-	- [`APIDescriptionType`](#apidescriptiontype)
-	- [`Error`](#error)
-		- [`UnknownJSONAPIError`](#unknownjsonapierror)
-		- [`BasicJSONAPIError`](#basicjsonapierror)
-		- [`GenericJSONAPIError`](#genericjsonapierror)
+    - [`ResourceBody`](#resourcebody)
+        - [nullable `PrimaryResource`](#nullable-primaryresource)
+    - [`MetaType`](#metatype)
+    - [`LinksType`](#linkstype)
+    - [`IncludeType`](#includetype)
+    - [`APIDescriptionType`](#apidescriptiontype)
+    - [`Error`](#error)
+        - [`UnknownJSONAPIError`](#unknownjsonapierror)
+        - [`BasicJSONAPIError`](#basicjsonapierror)
+        - [`GenericJSONAPIError`](#genericjsonapierror)
 - [`JSONAPI.Meta`](#jsonapimeta)
 - [`JSONAPI.Links`](#jsonapilinks)
 - [`JSONAPI.RawIdType`](#jsonapirawidtype)
 - [Sparse Fieldsets](#sparse-fieldsets)
-	- [Supporting Sparse Fieldset Encoding](#supporting-sparse-fieldset-encoding)
-	- [Sparse Fieldset `typealias` comparisons](#sparse-fieldset-typealias-comparisons)
+    - [Supporting Sparse Fieldset Encoding](#supporting-sparse-fieldset-encoding)
+    - [Sparse Fieldset `typealias` comparisons](#sparse-fieldset-typealias-comparisons)
 - [Replacing and Tapping Attributes/Relationships](#replacing-and-tapping-attributesrelationships)
-	- [Tapping](#tapping)
-	- [Replacing](#replacing)
+    - [Tapping](#tapping)
+    - [Replacing](#replacing)
 - [Custom Attribute or Relationship Key Mapping](#custom-attribute-or-relationship-key-mapping)
 - [Custom Attribute Encode/Decode](#custom-attribute-encodedecode)
 - [Meta-Attributes](#meta-attributes)
@@ -244,8 +244,8 @@ If your computed property is wrapped in a `AttributeType` then you can still use
 
 ### Copying/Mutating `ResourceObjects`
 `ResourceObject` is a value type, so copying is its default behavior. There are three common mutations you might want to make when copying a `ResourceObject`:
-1. Assigning a new `ID` to the copy of an identified `ResourceObject`.
-2. Assigning a new `ID` to the copy of an unidentified `ResourceObject`.
+1. Assigning a new `Id` to the copy of an identified `ResourceObject`.
+2. Assigning a new `Id` to the copy of an unidentified `ResourceObject`.
 3. Change attribute or relationship values.
 
 The first two can be accomplished with code like the following: