Tag, bump version, & update README.md

[rouson]

coverage on master

Summary of changes

Bumped the version number from 2.8.0 to 2.9.0 & updated README.md.

Rationale for changes

This is a release candidate.

Additional info and certifications

This pull request (PR) is a:

• Bug fix
• Feature addition
• Other, Please describe: release bump

I certify that

• I certify that:
  • I have reviewed and followed the contributing guidelines
  • I will wait at least 24 hours before self-approving the PR to give another
    OpenCoarrays developer a chance to review my proposed code
  • I have not introduced errant white space (no trailing white space or white space errors may
    be introduced)
  • I have added an explanation of what these changes do and why they should be included
  • I have checked to ensure there aren't other open Pull Requests for the same change
  • I have you written new tests for these changes
  • I have successfully tested these changes locally
  • I have commented any non-trivial, non-obvious code changes
  • The commits are logically atomic, self consistent and coherent
  • The commit messages follow best practices
  • Test coverage is maintained or increased after this is merged

Code coverage data

[codecov]

Codecov Report

Merging #709 into master will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #709 +/- ## ======================================= Coverage 54.53% 54.53% ======================================= Files 3 3 Lines 2923 2923 ======================================= Hits 1594 1594 Misses 1329 1329