vscode: enabe code analysis

[juarezr]

This PR has the objective of improving code analysis when using vscode

Changes

1. Configuring folders for vscode code analysis
2. Needs python extensions installed on vscode
3. Needs a python virtual environment with code analysis tools

Checklist

Use this checklist for assuring the quality of pull requests that include new code and or make changes to existing code.

• [ ] Source Code rules apply:
  • [ ] 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 are documented in docs/changes.rst
• [ ] Versioning and history tracking rules apply:
  • [ ] Using atomic commits when possible
  • [ ] Commits are reversible when possible
  • [ ] There is no incomplete changes in the pull request
  • [ ] There is no accidental garbage added in source code
• [ ] Testing rules apply:
  • [ ] Tested locally using tox / pytest
  • [x] Automated testing passes (see CI)
  • [x] Unit test coverage has not decreased (see Coveralls)
• [ ] State of these changes is:
  • [ ] Just a proof of concept
  • [ ] Work in progress / Further changes needed
  • [X] Ready to review
  • [X] Ready to merge

[coveralls]

Coverage remained the same at 91.759% when pulling 2ca7011422e87addfff3bbb81a5b29ba57c78f72 on juarezr:vscode-python-analysis into 1325d20806b86ff1880bed17d8302cfce918e755 on petl-developers:master.