[CMake] Documentation strategy

[Robert J. Hansen]

Brandon Van Every wrote:
> Also, students and other sorts of open source cheapskates do not buy
> books.

As a graduate student who knows a lot of other students (both graduate
and undergraduate), I can't accept this claim.  Between me and my
officemates, we probably have upwards of $5k in books we've purchased
with our own money on the office bookshelf.

Admittedly, the purchasing habits of graduate students may be different
from the purchasing habits of undergraduates, but even the
undergraduates in the department tend to buy books fairly frequently.