Update docs

Author: jtblin

CONTRIBUTING.md

@@ -4,7 +4,6 @@
 1. Fork the repo
 1. Install dependencies: `npm install` and `bower install`
 1. `npm run docker-build` to build the docker image
-1. Make your changes
-1. Install [GraphicsMagick](http://www.graphicsmagick.org/)
-1. Run linter and tests: `gulp check`
+1. Make your changes and add tests
+1. Run linter and tests: `npm run docker-test`
 1. Submit pull request

gulpfile.js

@@ -166,5 +166,5 @@
   gulp.task('deploy-patch', sequence('docker-test', 'bump-patch', 'assets', 'update', 'git-commit', 'git-push', 'npm'));
   gulp.task('deploy-minor', sequence('docker-test', 'bump-minor', 'assets', 'update', 'git-commit', 'git-push', 'npm'));
   gulp.task('deploy-major', sequence('docker-test', 'bump-patch', 'assets', 'update', 'git-commit', 'git-push', 'npm'));
-
+  
 })();