Selenium

* Fix doc of URL-related ExpectedCondition (6236)
* Added ExpectedCondition invisibility_of_element
* Swap out httplib for urllib3
* Be consistent with webdriver init kwarg service_log_path (5725)

* Add executing Chrome devtools command (5989)
* fix incorrect w3c action encoding in python client (6014)
* Implement context manager for WebDriver
* Stop sending "windowHandle" param in maximize_window command for w3c

* Add desired_capabilities keyword to IE and Firefox drivers for driver consistency
* Fix bug with creating Safari webdriver instance (5578)
* Add support for Safari extension command
* Deprecate Options `set_headless` methods in favor of property setter
* Only set --disable-gpu for Chrome headless when on Windows
* Add selenium User-Agent header (5696)
* Remote webdriver can now be started when passing options
* All Options.to_capabilities now start with default DesiredCapabilities
* Improve the error message that is raised when safaridriver cannot be found (5739)
* IeOptions class is now imported to selenium.webdriver
* Remove the beta `authenticate` methods from `Alert`

No changes just keeping python version in step with the rest of the project.

* make tests to check clicking on disabled element work for w3c compliant drivers (5561)
* add docstring for InvalidElementStateException. Fixes 5520
* Deleting unused imports
* Making python specification in IDEA project more generic
* It should be possible to use a custom safaridriver executable to run Selenium's test suite.

* Add docstrings to WebElement find methods (5384)
* Additional data in unexpected alert error is now handled for w3c drivers (5416)
* Allow service_args to be passed into Firefox WebDriver (5421)
* Fix bug introduced with response logging in 3.8.1 (5362)