Rewrite timeout handling code to support Selenium Server 3

[aik099]

1. Instead of supplying developer-provided timeout type directly to the Selenium Server as-is perform some validation as done in https://github.com/minkphp/webdriver-classic-driver .
2. Wrap WebDriver's TimeoutException and ScriptTimeoutException exceptions into DriverException, when the page wasn't opened due to page load/pageLoad timeout being met.
3. The pageLoad timeout wasn't working with Google Chrome on Selenium Server 3.

Closes #397

[aik099]

I've liked the deprecation of the page load and pageLoad timeout types from minkphp/webdriver-classic-driver#38 and probably will port in here as well.

[aik099]

I've liked the deprecation of the page load and pageLoad timeout types from minkphp/webdriver-classic-driver#38 and probably will port in here as well.

Done.