use q to replace Mr.Async in comparison.coffee
use q in viff.coffee to replace Mr.Async
remove Mr.Async in comparison.coffee
replace selenium-webdriver to wd

https://github.com/admc/wd/
optimise the Q promise structure
upgrade to 0.8.0
fix viff prehandler issue
update to 0.8.1
Merge pull request #25 from winsonwq/use-wd-to-replace-selenium-webdriver

Use wd to replace selenium webdriver