doc: sort string_decoder alphabetically

Reorders, with no contextual changes, the string_decode documentation
alphabetically.

PR-URL: #3662
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

Author: tflanagan

doc/api/string_decoder.markdown

@@ -19,10 +19,10 @@ additional support for utf8.
 
 Accepts a single argument, `encoding` which defaults to `utf8`.
 
-### decoder.write(buffer)
-
-Returns a decoded string.
-
 ### decoder.end()
 
 Returns any trailing bytes that were left in the buffer.
+
+### decoder.write(buffer)
+
+Returns a decoded string.