Deprecate webkit_debug driver
Deprecate webkit_debug driver

There's a configuration setting for this and having multiple, registered
drivers adds unnecessary complications.

addicted2sounds/capybara-webkit,nritholtz/capybara-webkit,twalpole/capybara-webkit,nritholtz/capybara-webkit,twalpole/capybara-webkit,thoughtbot/capybara-webkit,addicted2sounds/capybara-webkit,addicted2sounds/capybara-webkit,nritholtz/capybara-webkit,addicted2sounds/capybara-webkit,mhoran/capybara-webkit,mhoran/capybara-webkit,nritholtz/capybara-webkit,twalpole/capybara-webkit,thoughtbot/capybara-webkit,thoughtbot/capybara-webkit,twalpole/capybara-webkit,addicted2sounds/capybara-webkit,mhoran/capybara-webkit,nritholtz/capybara-webkit,thoughtbot/capybara-webkit,mhoran/capybara-webkit