Some additional configuration details in README file.

Adds some additional configuration details to the README file.  Still
lots more that could (should) be added.  Importantly, the new `pulse`
highlighting mechanism is detailed.
Update README.md

Add information about additional configuration variables.
Merge pull request #31 from T-J-Teru/more-readme

Add details on some configuration variables to README file.
Merge remote-tracking branch 'origin/master' into hl-inserted-style
Update the README file for changes to -highlight-inserted-item.

The control mechanism for highlighting inserted items has been
simplified, the README file is now up to date with these changes.