Adding Buffalo Linkstation NAS Login Scanner

I have added a login scanner for the Buffalo Linkstation
NAS.  I have been testing against version 1.68 of the
firmware.  Also included are some specs for this module.
Rescuing from JSON Parse

Previous code was not using any sort of exception handling
for parsing the response body.  I have added a rescue block
for JSON errors to remedy this problem.
Refactoring Success Case

I have refactored the code so that it will work with
non-root accounts.
Land #3987 - Buffalo Linkstation NAS Login Scanner