Add improved support for working with Google Sheets

[juarezr]

This PR has the objective of adding support to Google Sheets

Changes

1. Refactored #405
2. Renamed to/from-gsheet parameters.
3. Upgraded gspread support from v0.8 to v5.5
4. Improved the docs about the gsheet

Caveats

• CI needs a GCP account/Project
• May decrease coverage because of missing CI configuation

Checklist

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

• [X] Source Code rules apply:
  • [X] Includes unit tests
  • [X] New functions have docstrings with examples that can be run with doctest
  • [X] New functions are included in API docs
  • [x] ˜˜Docstrings include notes for any changes to API or behaviour˜˜
  • [ ] All changes are documented in docs/changes.rst
• [X] Versioning and history tracking rules apply:
  • [X] Using atomic commits when possible
  • [X] Commits are reversible when possible
  • [ ] There is no incomplete changes in the pull request
  • [ ] There is no accidental garbage added in source code
• [X] Testing rules apply:
  • [X] Tested locally using tox / pytest
  • [x] Automated testing passes (see CI)
  • [ ] Unit test coverage has not decreased (see Coveralls)
• [X] State of these changes is:
  • [ ] Just a proof of concept
  • [X] Work in progress / Further changes needed
  • [X] Ready to review
  • [ ] Ready to merge

[coveralls]

Pull Request Test Coverage Report for Build 1966632913

• 72 of 236 (30.51%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.05%) to 91.051%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
petl/io/gsheet.py	17	88	19.32%
petl/test/io/test_gsheet.py	52	145	35.86%
<!--	Total:	72	236	30.51%	-->

Totals
Change from base Build 1865160666:	-1.05%
Covered Lines:	12627
Relevant Lines:	13868

---

💛 - Coveralls

[arturponinski]

Great work, a nice feature and some test suite improvements. I do have a remark or an idea for follow up to issue, to improve the testability. What do you think about using vcr and casettes, in the same manner as gspread: https://github.com/burnash/gspread/tree/master/tests

[juarezr]

• Your proposal looks pretty interesting (if I got it correctly)
• How it would work?
• In this case, it would mock up web service calls replacing the need for a GCP account for testing?
• If so, please wait a little bit because I have some changes regarding batch API calls cooking yet.

[juarezr]

@arturponinski,

Can you take a look again, please? There are changes in API signatures, pytest and behavior...