feat(README): splitup the sections into individual files

The README is getting rather large so split it into individual files.

The next step will be rendering these into HTML pages with a TOC so that
they are a bit more navigable.

What do people think of this?
fix(README): link to the configuration file too
fix(Documentation): fixup headers

fixup the headers on the api and tuning sections
Merge pull request #440 from philips/splitup-README

feat(README): splitup the sections into individual files