Editorial: move "Path" to it's own section

spec/Section 7 -- Response.md

@@ -107,14 +107,8 @@ syntax element.
 If an error can be associated to a particular field in the GraphQL result, it
 must contain an entry with the key `path` that details the path of the response
 field which experienced the error. This allows clients to identify whether a
-`null` result is intentional or caused by a runtime error.
-
-If present, this field must be a list of path segments starting at the root of
-the response and ending with the field associated with the error. Path segments
-that represent fields must be strings, and path segments that represent list
-indices must be 0-indexed integers. If the error happens in an aliased field,
-the path to the error must use the aliased name, since it represents a path in
-the response, not in the request.
+`null` result is intentional or caused by a runtime error. The value of this
+field is described in the [Path](#sec-Path) section.
 
 For example, if fetching one of the friends' names fails in the following
 operation:
@@ -244,6 +238,19 @@ discouraged.
 }
 ```
 
+### Path
+
+A `path` field allows for the association to a particular field in a GraphQL
+result. This field must be a list of path segments starting at the root of the
+response and ending with the field to be associated with. Path segments that
+represent fields must be strings, and path segments that represent list indices
+must be 0-indexed integers. If the path is associated to an aliased field, the
+path must use the aliased name, since it represents a path in the response, not
+in the request.
+
+When the `path` field is present on an "Error result", it indicates the response
+field which experienced the error.
+
 ## Serialization Format
 
 GraphQL does not require a specific serialization format. However, clients