Stop testing Dartium on Travis (#46)

diff --git a/.travis.yml b/.travis.yml
index 04b3dd1..cde2825 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,13 +1,12 @@
 language: dart
-sudo: false
+
 dart:
   - stable
   - dev
+
 dart_task:
   - test: -p vm
   - test: -p firefox
-  - test: -p dartium
-    install_dartium: true
   - dartfmt
   - dartanalyzer