Prompt Users to Enable Password Sage in Incognito

Many users will not know that extensions do not run in incognito mode by default and some are even prone to using incognito mode for engaging in riskier activity.

We can detect when we are not enabled for incognito mode (at install?) and prompt the user to enable Password Sage in Incognito mode:

http://stackoverflow.com/questions/17438354/how-can-i-enable-my-chrome-extension-in-incognito-mode