Revert "docs: Fix ABI/API confusion on "what makes buck so fast" page."

This reverts commit 6243308a434305096ed91b0b5c764c46e5e734c8.

Going to reland this with the correct author.
docs: Fix ABI/API confusion on "what makes buck so fast" page.

Summary:
Closes #115

Also added missing <p> tags.  The paragraphs without a leading <p>
were smooshed together.

Test Plan: Visually checked result with "soyweb-local.sh" server and Chrome.