r-wdman 0.2.5 Webdriver/Selenium binary manager

There are a number of binary files associated with the Webdriver/Selenium project (see http://www.seleniumhq.org/download/, https://sites.google.com/a/chromium.org/chromedriver/, https://github.com/mozilla/geckodriver, http://phantomjs.org/download.html, and https://github.com/SeleniumHQ/selenium/wiki/InternetExplorerDriver for more information). This package provides functions to download these binaries and to manage processes involving them.