Modify the benchmark installer to download the dart SDK.

installer.py

@@ -37,6 +37,11 @@ class Installer:
     # Languages
     #######################################
 
+    #
+    # Dart
+    #
+    self.__run_command("curl https://storage.googleapis.com/dart-editor-archive-integration/latest/dartsdk-linux-64.tar.gz | tar xvz")
+
     #
     # Erlang
     #