fix benchmarks after breaking marshaller changes
Merge pull request #248 from yjbanov/fix-benchmarks

fix benchmarks after breaking marshaller changes
reinstate dart2js transformers now that dart2js is lazy
Merge pull request #250 from yjbanov/fix-benchmarks

reinstate dart2js transformers now that dart2js is lazy
Changes.
Add protoc option to apigen.
TODO for protoc default value pinning.
Merge pull request #252 from alxhub/protoc-path

Allow specifying path to protoc in apigen.dart.