perf(ProtoRecord): remove the unused prev field
perf(ProtoRecordRange): re-use a ProtoRecordCreator
feat(examples): adds static dart hello world example.

Use gulp examples/pub.serve to start up the server and go to
http://localhost:8080/index_static.html to see the static app.
fix(record-range): fixes bug when disabling empty ranges.
feat(change_detector): notify directives on property changes
perf(change_detection): add baseline to change detection benchmark
chore(gulp): Skip Dart tasks when the SDK is not detected

fixes #268