Made fixes from the PR from jvazquez-r7

The get_once would *only* return "MMcS", and stop. I
modified it to be a get(3, 3). Additionally, the command
length was set to 0x01 when it needed to be 0x00.
Land #2843, RangeWalker resolution failure bug fix
Fix the closing brackets on the banner.
Add a link to http://bit.ly/msfsurvey in banner
Land #2848, @sho-luv's MS08-067 scanner
Move back the expires date.
Code Review Feedback

Removed the parameters from get() since it works without them
Fix beug with #next raising after the end

... instead of the old behavior or just returning nil again
Better docs, more accurate var names
Replace unused var with purpose-revealing comment
Fix indentation
Land #2822, @mandreko's aux module for OSVDB 101653
dangit odd number of ]s
Delete parentheses
Add spec for fixed bug
Land #2853, user survey banner splat
Land #2854, #next nil beug fix
Use 'unless' instead of 'if not'
Land #2855, Rex::Socket refactor and specs
Correct a typo

They caught me. Thanks HD.