Beamer compatibility

[hoodmane]

Doug says:

If you write code for a spectral sequence within a frame, the results will not be what you hope for, even if the sseq code is correct and works fine a separate test file. You should instead write this code BETWEEN FRAMES (so Beamer itself does not try to process it), and just put the printpage command in the frame environment.

A paragraph about this in your manual could save some users a LOT of grief.