Update README.md

Verison -> Version

Author: lundstrj

README.md

@@ -77,7 +77,7 @@ from appium import webdriver
 
 desired_caps = {}
 desired_caps['platformName'] = 'iOS'
-desired_caps['platformVerison'] = '7.1'
+desired_caps['platformVersion'] = '7.1'
 desired_caps['deviceName'] = 'iPhone Simulator'
 desired_caps['app'] = PATH('../../apps/UICatalog.app.zip')