Move README.md to user_manual.md
Made docs/README.md be a directory of what we have.
Make top level README source links relative.

This way things work if you're on a branch.  Also fix link
to the user manual.
Show which arguments are optional
Merge pull request #133 from spotify/drewc/doc-rework

Make the docs/ directory a little easier to use/make sense of
Updated testing framework doc to use service registration/discovery