Cheat sheet fixes

[ned14]

Change:
Boost.AFIO version 1.4 provides the following operations:

To:

Boost.AFIO version 1.4 provides the following operations: (number of
overloads)

BUT, do you need to tell us this? I think a "YES" in the cells where you
have numbers is all we need to know. There is already too much information
on this page, considering it is supposed to be a "single page cheat
sheet".

The art in technical writing is to remove as much as possible from your
first full draft. E.g. your first two bullet points could instead be:

• AFIO models file handles as a reference counted std::shared_ptr

  ** handle could represent a closed file descriptor/handle, not just an
  open one.

  ** You can create your own custom implementations of handle.

• AFIO models a filesystem as a reference counted
  std::shared_ptr

  ** When constructed using make_dispatcher() you specify a URI such as
  file:///.

  ** You can create your own custom dispatcher implementations.

HTH,