Remove 'chromedriver' from dependencies

Please note that it is just a (rather broken) Python package.
Its purpose is solely to download a `chromedriver` binary
from the Google servers and make it discoverable by simply importing
the module.

The reason for removal is that it currently breaks the build process
and pulls a very outdated version.

If you wish to use the test suites with the Chrome / Chromium browser,
you should manually install a `chromedriver` binary of an appropriate
version into one of your `$PATH` directories.

-from chromedriver import CHROMEDRV_PATH
-from robot import run_cli
 import os
 import sys
-
-sys.path.append(CHROMEDRV_PATH)
+from robot import run_cli
 
 
 def runner():

@@ -22,7 +22,6 @@ setup(name='op_robot_tests',
           'Pillow',
           'PyYAML',
           'barbecue',
-          'chromedriver',
           'dateutils',
           'dpath',
           'haversine',