Replace README.txt with README.md

Reviewed MR!3, the patch is not cleanly applied.

a. git.drupalcode.org_project_supermonitoring_-_merge_requests_3.diff.txt:12: trailing whitespace.

git.drupalcode.org_project_supermonitoring_-_merge_requests_3.diff.txt:20: trailing whitespace.
  into Drupal admin panel, enabling you to view reports
git.drupalcode.org_project_supermonitoring_-_merge_requests_3.diff.txt:21: trailing whitespace.
  and configure services without the need to leave your CMS
warning: 3 lines add whitespace errors.
b. Change "## Contents Of This File" to "## Table of contents"
c. Project Name is missing.
d.[Project page] and [issue queue] is missing.
e. Requirement and Configuration both are the mandatory fields but both are missing.

I have added the missing sections. Content to be added.