Replace docker with a directly launched Chrome for integration tests

The benefits:

- Speed up chrome tests (from 160s to 34s on my machine).
- Allow us to remove docker, which caused quite a few headaches.
- Gets us a more current Chrome, so now we run tests against all
  supported versions.
- We don't touch the FS anymore.
- We no longer depend on sudo for travis, which means we can use
  their new container-based infrastructure. This also speeds up our
  tests :)

Tests are now implemented in javascript; the server detects when
they are complete and kills Chrome.

Fixes #417.

.travis.yml

@@ -1,4 +1,4 @@
-sudo: required
+dist: trusty
 
 addons:
   hosts:
@@ -6,9 +6,6 @@ addons:
 
 language: go
 
-services:
-  - docker
-
 go:
   - 1.7.x
   - 1.8.x
@@ -30,6 +27,8 @@ before_install:
   - go get github.com/onsi/gomega
   - export GOARCH=$TRAVIS_GOARCH
   - go env # for debugging
+  - "export DISPLAY=:99.0"
+  - "Xvfb $DISPLAY &"
 
 script:
   - .travis/script.sh