Prepare first upload to PyPI

[HealthyPear]

This PR prepares the first release that will be uploaded to PyPI as v0.4.0.post1 by updating the setup.py in a way that a pure pip installation will be possible with tests and docs extra requirements.

It is a requirement for PR #105.

It also comes with the following modifications:

• updated installation instructions for both released and development versions
• updated .zenodo.json with changes that hopefully will unlock the DOI generation which got stuck with v0.4.0
• updated README
• fix .gitignore for dummy files generated by setup.py and related to versioning

[codecov[bot]]

Codecov Report

Merging #107 (a82f151) into master (92f3120) will increase coverage by 0.03%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #107      +/-   ##
==========================================
+ Coverage   37.03%   37.06%   +0.03%     
==========================================
  Files          19       20       +1     
  Lines        1801     1802       +1     
==========================================
+ Hits          667      668       +1     
  Misses       1134     1134              

Impacted Files	Coverage Δ
protopipe/__init__.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 92f3120...a82f151. Read the comment docs.