Reduce crash rate on .get() in general

[dreisman]

Examples of crashes:

File "/home/ubuntu/openwpm-census/OpenWPM/automation/BrowserManager.py", line 298, in BrowserManager
extension_socket)
File "/home/ubuntu/openwpm-census/OpenWPM/automation/Commands/command_executor.py", line 14, in execute_command
browser_params=browser_params, extension_socket=extension_socket)
File "/home/ubuntu/openwpm-census/OpenWPM/automation/Commands/browser_commands.py", line 91, in get_website
webdriver.get(url)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 245, in get
self.execute(Command.GET, {'url': url})
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 231, in execute
response = self.command_executor.execute(driver_command, params)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/remote_connection.py", line 395, in execute
return self._request(command_info[0], url, body=data)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/remote_connection.py", line 426, in _request
resp = self._conn.getresponse()
File "/usr/lib/python2.7/httplib.py", line 1051, in getresponse
response.begin()
File "/usr/lib/python2.7/httplib.py", line 415, in begin
version, status, reason = self._read_status()
File "/usr/lib/python2.7/httplib.py", line 379, in _read_status
raise BadStatusLine(line)
BadStatusLine: ''

[dreisman]

UnexpectedAlertPresentException: Alert Text: A script on this page may be busy, or it may have stopped responding. You can stop the script now, open the script in the debugger, or let the script continue.

Script: http://www.sankei.com/apr_comm\u2026v1/common/jquery-1.11.1.min.js:2
Message: Unexpected modal dialog (text: A script on this page may be busy, or it may have stopped responding. You can stop the script now, open the script in the debugger, or let the script continue.

[englehardt]

Many of these errors are caused by Selenium 2's FirefoxDriver browser extension. With the move to Selenium 3 / Marionette in #152 we should check if the error rate has reduced.

[englehardt]

Closing in favor of #255 now that we've moved to geckodriver and webextensions.