pkg/protobuf: cleanup and prep for 0.3.5 release

README.md

-Protobuf runtime support library
-================================
+Provides runtime support for a Dart implementation of protobufs.
 
 [![Build Status](https://drone.io/github.com/dart-lang/dart-protobuf/status.png)](https://drone.io/github.com/dart-lang/dart-protobuf/latest)
 
-This library provides runtime support library for Dart implementation
-of protobufs.
+Typically one do not need to import this library–only libraries
+generated by the protoc plugin import this library directly.
 
-Typically one do not need to import this library---only libraries
-generated by protoc plugin import this library directly.
+If your library or application uses generated protobuf libraries, add this
+library as a dependency.
 
-However, if your library or application uses generated protobuf libraries,
-please, add this library as a dependency.
+### References
 
-Hacking
--------
-
-So far to hack on the library the main thing you should be aware of is how
-to run unittests.  The easiest way would be to use DartEditor and run
-`all_tests.dart` file which is the whole suite.
-
-If you'd like to run test from command line, please, do not pass proper
-package root.
-
-Useful references
------------------
-
-* [Main Dart site](http://www.dartlang.org)
-* [Main protobuf site](https://code.google.com/p/protobuf)
+* [protobuf site](https://code.google.com/p/protobuf)
 * [Protoc plugin project](https://github.com/dart-lang/dart-protoc-plugin)
-* [DartEditor download](http://www.dartlang.org)
-* [Pub documentation](http://pub.dartlang.org/doc)