Forgot to fill in the dates

CHANGELOG.txt

-nanopb-0.3.8 (2016-03-xx)
+nanopb-0.3.8 (2017-03-05)
  Fix problems with multiple oneofs in same message (#229)
  Zero-valued extension fields were mistakenly ignored by encoder (#242)
  Multiple fixes related to proto3 mode (#242, #245, #247, #249)

docs/migration.rst

@@ -11,7 +11,7 @@ are included, in order to make it easier to find this document.
 
 .. contents ::
 
-Nanopb-0.3.8 (2017-xx-xx)
+Nanopb-0.3.8 (2017-03-05)
 =========================
 Fully drain substreams before closing