changes for 0.3.9

CHANGELOG.md

+## 0.3.9
+ * Add experimental mixins_meta library
+ * Add experimental PbMapMixin class (in a separate library).
+ * Fix bug where ExtensionRegistry would not be used for nested messages.
+
 ## 0.3.7
  * More docs.
 
 ## 0.3.6
  * Added mergeFromMap() and writeToJsonMap()
  * Fixed an analyzer warning.
 
 ## 0.3.5+3
  * Bugfix for `setRange()`: Do not assume Iterable has a `sublist()` method.
 
 ## 0.3.5+2
  * Simplify some types used in is checks and correct PbList to match the
  * signature of the List setRange method.
 
 ## 0.3.5+1
 
  * Bugfix for incorrect decoding of protobuf messages: Uint8List views with
    non-zero offsets were handled incorrectly.
 
 ## 0.3.5
 
  * Allow constants as field initial values as well as creation thunks to reduce
    generated code size.
 
  * Improve the performance of reading a protobuf buffer.
 
  * Fixed truncation error in least significant bits with large Int64 constants.