Add docs for Str.kind (#57)

Author: ilevkivskyi

typed_ast/ast27.py

@@ -19,9 +19,8 @@
       called with `mode=func_type`.
     - `Module` has a `type_ignores` field which contains a list of
       lines which have been `# type: ignore`d.
-    - `Str` has a `has_b` boolean field which indicates if the string is
-      explicitly prefixed with a `b`. (This is deprecated and may be removed in
-      future versions.)
+    - `Str` has a `kind` string field which preserves the original string
+      prefix, so that `ast27.parse('br"test"').body[0].value.kind == 'br'`.
 
     An abstract syntax tree can be generated by using the `parse()`
     function from this module.  The result will be a tree of objects whose

typed_ast/ast3.py

@@ -21,6 +21,8 @@
       newer Python syntax features.
     - `Module` has a `type_ignores` field which contains a list of
       lines which have been `# type: ignore`d.
+    - `Str` has a `kind` string field which preserves the original string
+      prefix, so that `ast3.parse('u"test"').body[0].value.kind == 'u'`.
 
     An abstract syntax tree can be generated by using the `parse()`
     function from this module.  The result will be a tree of objects whose