DOCS-2643: Clarify distinction between positional $ and projection $elemMatch.

Signed-off-by: kay <kay.kim@10gen.com>
Adds in PyYAML requirement to README

Signed-off-by: kay <kay.kim@10gen.com>
Use the term "32 bit limitation page"

"32 bit limitations for" sounds wrong, "32 bit limitations page" sounds better

Signed-off-by: kay <kay.kim@10gen.com>
fix: include directory