Update chromedriver to 2.15
Update chromedriver to 2.15

From https://chromedriver.storage.googleapis.com/index.html?path=2.15/
```
----------ChromeDriver v2.15 (2015-03-26)----------
Supports Chrome v40-43
```
appium/appium,appium/appium,appium/appium,Sw0rdstream/appium,appium/appium,appium/appium,appium/appium