Add ability to inquire for password

[nickbabcock]

Not sure how you want to do this, but added the ability to inquire for passwords if the user says that there is a password. I found this convenient because I would rather enter in the password every time rather than store the password someplace.

ex

      scp: {
          options: {
              host: '<<host>>',
              username: '<<username>>',
              password: true
          },
         // ...
       }