Added functionality to bypass alerts

This is done with the following steps:
'I confirm all alerts' means that all alert and confirm windows are returned and returned true respectively
'I dismiss all alerts' means that all confirm windows are returned false
'I answer all prompts with "([^"]*)"' means that all prompts are returned with the given string

Please note that these settings are on a PER PAGE basis.  This means that for best results, the step must be given right before the alert is generated.
Fixed other scenarios that were skipped
Fixed tab issue (tabs are now correctly spaces)
Fixed wording in the step
Small wording fix
Changed wording to I will
Added docstring specifying when this method must be called
Merge pull request #77 from edx/jonahstanley/fix-alert-tests

Jonahstanley/fix alert tests