Added new method to change passwords for existing logins
Added the ability to Change Passwords in 1Password
Use the password generator options when changing passwords.
Remaned to `kUTTypeAppExtensionChangePasswordAction ` + fixed copy/paste error message
Making sure that we don't pass a nil username
Merge pull request #52 from AgileBits/feature/add-the-ability-to-change-passwords

[NEW] Added the ability to Change Passwords in 1Password.