Dart build status

Add build status badge for Dart

README.md

@@ -63,7 +63,7 @@ how to install protobuf runtime for that specific language:
 | Ruby                                 | [ruby](ruby)                                                | [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-ruby_all.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2Fruby_all%2Fcontinuous) | [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-ruby21.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fruby21%2Fcontinuous)<br/>[![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-ruby22.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fruby22%2Fcontinuous) | |
 | Go                                   | [golang/protobuf](https://github.com/golang/protobuf)       | | | |
 | PHP                                  | [php](php)                                                  | [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-php_all.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2Fphp_all%2Fcontinuous)<br/>[![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-32-bit.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2F32-bit%2Fcontinuous) | [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-php5.6_mac.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fphp5.6_mac%2Fcontinuous)<br/>[![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-php7.0_mac.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fphp7.0_mac%2Fcontinuous) | |
-| Dart                                 | [dart-lang/protobuf](https://github.com/dart-lang/protobuf) | | | |
+| Dart                                 | [dart-lang/protobuf](https://github.com/dart-lang/protobuf) | [![Build Status](https://travis-ci.org/dart-lang/protobuf.svg?branch=master)](https://travis-ci.org/dart-lang/protobuf) | | |
 
 Quick Start
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