Add substitution-permutation network to glossary
Some work on the AES sections
Add an advanced section marker
Fix footnote about differential attacks in AES section
Mark Rijndael in-depth section as advanced
Fix some of HMMs review points
Fix advanced marker

The \caption command was being used outside of a figure.
Mark the Montgomery ladder derivation as advanced
Merge branch 'master' of github.com:crypto101/book