Fix Markdown syntax and fine tune documentation

[joeangel]

• Fix Markdown syntax
  • Before:
  • 
  • After:
  • 
• Fine tune documentation
  • Remove ending spaces in the documentation
  • Remove an unnecessary heading in the documentation

[joeangel]

send PR to https://github.com/flash-oss/node_acl/pull/13

This acl project is maintained by https://github.com/flash-oss/node_acl