Use entrypoints to install petablint as a command

[cthoyt]

• Added missing requirement "colorama"
• Update README.md accordingly
• Move /bin/petablint.py into main module and add Python entrypoint

Now it's possible to call petablint like any other unix command (e.g., grep, cat, etc.). Python automatically takes care of this when pip installing.

[codecov-io]

Codecov Report

Merging #85 into develop will decrease coverage by 5.43%.
The diff coverage is 9.09%.

@@             Coverage Diff             @@
##           develop      #85      +/-   ##
===========================================
- Coverage    59.17%   53.74%   -5.44%     
===========================================
  Files            5        6       +1     
  Lines          632      694      +62     
  Branches       136      147      +11     
===========================================
- Hits           374      373       -1     
- Misses         230      293      +63     
  Partials        28       28

Impacted Files	Coverage Δ
petab/petablint.py	0% <0%> (ø)
petab/core.py	70.96% <20%> (-0.1%)	⬇️

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[yannikschaelte]

looks great, thanks!

Could you change the target to ICB-DCM:develop instead of master (following a develop/master branching structure)?

[cthoyt]

@yannikschaelte good call! I didn't realize that you had the develop/master dichotomy. Perhaps it might be helpful for new developers to make the develop branch the default one.

I've merged the changes from develop into this branch then pointed the merge to the develop branch. Looks like one of the changes (adding the colorama requirement) had even already been fixed!