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
  • Ready to review
  • Ready to merge

[coveralls]

Coverage remained the same at 91.759% when pulling e0e2a27 on juarezr:github-pr-template into 552808d on petl-developers:master.