Add support for downloading nw.js' Chromedriver

[twolfson]

In nwjs/npm-installer#23, we are discussing what repository best fits downloading nw.js' Chromedriver. It was recently mentioned that Selenium can take a custom path for both Chromedriver binary as well as Chrome binary. Would it be possible to add another download option for nw.js' Chromedriver?

[pose]

@twolfson Yes, definitely. We can add a new property here called nw-chromedriver: https://github.com/pose/webdriver-manager/blob/master/config.json#L3 . What do you think?

[twolfson]

Yea, I think that would work.

[gbmhunter]

Looks good.

[twolfson]

Awesome, thanks @pose. I will try it right out =)

[twolfson]

It looks like the latest release is installing chromedriver instead of chromedriver-nw =/

$ ./node_modules/.bin/webdriver-manager update --chromedriver-nw
Updating selenium standalone
downloading http://selenium-release.storage.googleapis.com/2.46/selenium-server-standalone-2.46.0.jar...
Updating chromedriver
downloading http://chromedriver.storage.googleapis.com/2.16/chromedriver_linux64.zip...
chromedriver_2.16.zip downloaded to /home/todd/github/plaidchat/node_modules/webdriver-manager/selenium/chromedriver_2.16.zip
/home/todd/github/plaidchat/node_modules/webdriver-manager/selenium/chromedriver_2.16.zip /home/todd/github/plaidchat/node_modules/webdriver-manager/selenium
selenium-server-standalone-2.46.0.jar downloaded to /home/todd/github/plaidchat/node_modules/webdriver-manager/selenium/selenium-server-standalone-2.46.0.jar
The following files were installed: /home/todd/github/plaidchat/node_modules/webdriver-manager/selenium/selenium-server-standalone-2.46.0.jar /home/todd/github/plaidchat/node_modules/webdriver-manager/selenium/chromedriver

[twolfson]

I found the issue and am opening a patch for it.