refactor(karma): start chrome headless without sandbox

This is required by Travis to run our tests in the containerized
environment.

.travis.yml

@@ -13,10 +13,6 @@ cache:
   directories:
     - node_modules
 
-before_script:
-  - "sudo chown root /opt/google/chrome/chrome-sandbox"
-  - "sudo chmod 4755 /opt/google/chrome/chrome-sandbox"
-
 script:
   - npm run-script test-node
   - if [[ $(node --version) != v4* ]] ; then npm run-script test-browser; fi

karma.conf.js

@@ -39,9 +39,6 @@ const onwarn = warning => {
 
 rollupConfig.onwarn = onwarn;
 
-// Karma configuration
-// Generated on Thu Jun 28 2018 14:24:01 GMT-0400 (EDT)
-
 module.exports = function(config) {
   config.set({
     basePath: '',
@@ -56,7 +53,13 @@ module.exports = function(config) {
     colors: true,
     logLevel: config.LOG_INFO,
     autoWatch: true,
-    browsers: ['ChromeHeadless'],
+    browsers: ['ChromeHeadlessNoSandbox'],
+    customLaunchers: {
+      ChromeHeadlessNoSandbox: {
+        base: 'ChromeHeadless',
+        flags: ['--no-sandbox']
+      }
+    },
     singleRun: true,
     concurrency: Infinity
   });