chromium webdeiver
$ sudo apt-get install chromium-chromedriver
$ sudo ln -s /usr/lib/chromium-browser/chromedriver /usr/bin/chromedriver
add ~/.bashrc
export PATH=$PATH:/usr/lib/chromium-browser/
Selenium::WebDriver::Chrome.path = '/usr/lib/chromium-browser/chromium-browser'
driver = Selenium::WebDriver.for :chrome
a = Watir::Browser.new driver