Improve book comparison script

[anematode]

Currently, the output of ./scripts/compare_books.py is an eyesore:

Timoothy:gatm timoothy$ python2 ./scripts/compare_books.py | grep "02" -A 1
Chapter 02 It's a Snap, Problem 8: Notice that $E\snap E\snap E=I$ (see Figure~\ref{fig:eper3}). We saw that $E$ has a \textbf{period} of $3$ when acting upon itself. Which elements have a period of
ANSWER KEY: Problem 8: Notice that $E\snap E\snap E=I$ (See Figure~\ref{fig:eper3}). We see that $E$ has a \textbf{period} of $3$ when acting upon itself. Which elements have a period of
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Chapter 02 It's a Snap, Problem 9: Answer the following with the one-, two-, and four-post snap groups $S_1$, $S_2$ and $S_4$. These are just the analogous groups for connections between rows of one, two, and four posts.
ANSWER KEY: Problem 9: Answer the following with the one-, two-, and four-post snap groups $S_1$, $S_2$ and $S_4$. These are just the analogous groups for connections between one, two, and four posts.
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Chapter 02 It's a Snap, Problem 9.c: Make a group table of these elements. For four posts, instead of creating a table, give the number of entries that the table would have.
ANSWER KEY: Problem 9.c: Make a group table of these elements. For four posts, instead of creating a massive table, give the number of elements that the table would have.

In particular, you need to scan each line to see where the differences are, and the lines aren't even lined up. Ideally the lines would be lined up and a diff shown.