Stop testing on Dartium (#4)

diff --git a/.travis.yml b/.travis.yml
index 61ef6f5..610bd03 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,8 +7,6 @@
   - test: -p vm
     xvfb: false
   - test: -p firefox
-  - test: -p dartium
-    install_dartium: true
   - dartanalyzer
 
 matrix: