Add README.md

[vipulgupta2048]

The documentation of this activity has been migrated from the wiki.
Check for more information godiard/help-activity/pull/43

This PR adds a basic README where 'How to use Ruler' points to the migrated user-documentation.

Feel free to add/subtract information as necessary from the README.md file

Status - Merge after godiard/help-activity/pull/43 gets merged

[quozl]

Reviewed to 2ab156a.

• copy and paste error; dangling reference to Turtle Confusion,
• commit message is very brief and does not use imperative mood, see making commits.
• activity fails to work, per Fails with Fedora 28 #4, Fails with Ubuntu 16.04 sucrose #3, and now Fails with Ubuntu 18.04 #6, so time invested in a README.md seems wasted.

[vipulgupta2048]

• Fixed the reference, fixed some more things in README.md
• Commit message amended
• I wouldn't call it wasted 😄 mistakes teach like these teach me to be more considerate and not rush into things. I should have completely understood the state of the activity before implementing the migration script. Also, this finds me my new tasks to work and contribute on. I request the PR to remain open until the issues are resolved as mentioned in Migrate Ruler documentation from Wiki godiard/help-activity#43
  Thanks

[quozl]

Thanks.