Update readme.rst

Run tests section does not render on github correctly and this information is available in docs.

Problem

The readme.rst tests section does not render on github and this information is already available in the documentation.

Solution

Removed the section heading and related Run Tests section from readme.rst.

Commandments

• Write PEP8 compliant code.
• Cover it with tests.
• Update CHANGES.rst file to describe the changes, and quote according issue with GH-<issue_number>.
• Pay attention to backward compatibility, or if it breaks it, explain why.
• Update documentation (if relevant).