Remove "Gen'd by DocToc" ToC line in README
The very first line of the README, an important place, is this useless
line. Better to remove it and let users see content first.
DocToc doesn't re-add the line when updating the table of contents.
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
-**Table of Contents** *generated with [DocToc](https://github.com/thlorenz/doctoc)*
+
- [Submariner](#submariner)
- [Architecture](#architecture)
