Remove Dartium runs from Travis (flutter#68)

Now fails on dev latest

Author: kevmoo

.travis.yml

@@ -1,20 +1,21 @@
 language: dart
-sudo: false
+
 dart:
   - dev
   - stable
-cache:
-  directories:
-    - $HOME/.pub-cache
+
 dart_task:
   - test: --platform vm
   - test: --platform firefox -j 1
-  - test: --platform dartium
-    install_dartium: true
   - dartanalyzer
   - dartfmt
+
 matrix:
   # Only run dartfmt checks with stable.
   exclude:
     - dart: dev
       dart_task: dartfmt
+
+cache:
+  directories:
+    - $HOME/.pub-cache