chore(travis): use test matrix

.travis.yml

@@ -5,18 +5,31 @@ language: node_js
 node_js:
   - 0.10
   - 0.11
+env:
+  global:
+    - SAUCE_LABS=false PARSER=false OPTIONS=""
+  matrix:
+    - PARSER="traceur"
+    - PARSER="6to5"
+matrix:
+  include:
+    - node_js: "0.10"
+      env: SAUCE_LABS=true PARSER="traceur"
+    - node_js: "0.10"
+      env: SAUCE_LABS=true PARSER="6to5"
+    - node_js: "0.10"
+      env: SAUCE_LABS=true PARSER="traceur" OPTIONS="--ie8"
+    - node_js: "0.10"
+      env: SAUCE_LABS=true PARSER="6to5" OPTIONS="--ie8"
 before_install:
   - export CHROME_BIN=chromium-browser
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
   - npm update -g
   - npm install -g karma-cli grunt-cli
-script:
+before_script:
   - grunt
-  - npm test
-  - npm run test:browser-traceur
-  - npm run test:browser-6to5
-  - npm run test:browser-traceur -- --saucelabs
-  - npm run test:browser-6to5 -- --saucelabs
-  - npm run test:browser-traceur -- --saucelabs --ie8
-  - npm run test:browser-6to5 -- --saucelabs --ie8
+script:
+  - npm run test:node
+  - npm run test:browser-$PARSER
+  - "[ $SAUCE_LABS == false ] || npm run test:browser-$PARSER -- --saucelabs $OPTIONS"