Added CpdtTactics

Proof automation is nice, and I needed some of it for the Palindromes
exercise
Updated SfLib.v

This was missing some important things, and Omega wasn't exporting.
Now neither of those things are true.
Solved Palindromes Problems

I actually had to move this to a separate file because I wanted to use
SfLib and the proof was getting a bit unwieldy
Something tells me this isn't the simplest solution, but AFAIK it's the
first one uploaded publicly, so there's that
Completed Imp Chapter

Lots of optional exercises I'll have to get back to later though