GitHub pr template

[juarezr]

This PR has the objective of updating GitHub docs reflecting ci migration.

Changes

1. Added new CI/CD badges
2. Updated PR template

Checklist

Checklist for pull requests including new code and/or changes to existing code.

• [ ] Code
  • [ ] Includes unit tests
  • [ ] New functions have docstrings with examples that can be run with doctest
  • [ ] New functions are included in API docs
  • [ ] Docstrings include notes for any changes to API or behaviour
  • [ ] All changes documented in docs/changes.rst
• [ ] Testing
  • [ ] (Optional) Tested local against remote servers
  • [ ] Travis CI passes (unit tests run under Linux)
  • [ ] AppVeyor CI passes (unit tests run under Windows)
  • [ ] Unit test coverage has not decreased (see Coveralls)
• [ ] Changes
  • [ ] (Optional) Just a proof of concept
  • [ ] (Optional) Work in progress
  • [X] Ready to review
  • [X] Ready to merge

[coveralls]

Coverage remained the same at 91.759% when pulling e0e2a27e7edcb1e94f7e04f87d31b69e9244cbc7 on juarezr:github-pr-template into 552808daccc4d46916c385b582b6b8fbdc81f8f1 on petl-developers:master.