major workflow updates

* changed to using a more comprehensively built image with ready-made
  chrome w/ chromedriver
* using host shared memory mounted as a volume as per recommendation
* run headlessly

.drone.yml

@@ -8,13 +8,20 @@ platform:
 steps:
 - name: open-website
   pull: always
-  image: robotframework/rfdocker
+  image: selenium/node-chrome
+  volumes:
+  - name: shm
+    path: /dev/shm
   commands:
   - uname -r
   - python --version
   - ls -la
-  - pip install robotframework-seleniumlibrary
-  - robot test001.robot
+  - START_XVFB=false robot test001.robot
   - cat log.html
   - cat output.html
   - cat report.hmtl
+
+volumes:
+- name: shm
+  host:
+    path: /dev/shm