Made sizes change dynamically

I was getting tired of calculating and changing a million variables
every time I decided the spines were too short, so I went ahead and
coded some jQuery that sets the spine height (width), margins, offsets,
etc. from a single variable ('spineWidth' at ln. 63 of main.js). I
should probably do the same thing for heights, but I like them how they
are right now so no big. Also, I fixed the dynamically generated width
of the records div.