Updating README.md
Updating README.md

* Added info that demonstrates this utility has the ability to
  choose between running this as "git-quick-stats" or
  "git quick-stats" as requested in Issue #77
* Adjusted Table of Contents to show all sections and subsections
  of the README.md
* Cleaned up some grammar and added some extra info in various
  places
* Ran through VS Code's markdownlint extension and adjusted some
  syntax accordingly

arzzen/git-quick-stats