[WIP] Tutorial docs fixes

[nazarewk]

So i am going through buildbot tutorial and updating docs on the way, still work in progress.

• I have created a file in the master/buildbot/newsfragment directory (and read the README.txt in that directory)
• I have updated the appropriate documentation

[mention-bot]

@nazarewk, thanks for your PR! By analyzing the history of the files in this pull request, we identified @lsblakk, @rutsky and @benallard to be potential reviewers.

[codecov]

Codecov Report

Merging #3159 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3159      +/-   ##
==========================================
- Coverage   88.06%   88.05%   -0.01%     
==========================================
  Files         314      317       +3     
  Lines       33046    33146     +100     
==========================================
+ Hits        29101    29187      +86     
- Misses       3945     3959      +14

Impacted Files	Coverage Δ
master/buildbot/steps/cmake.py	100% <0%> (ø)	⬆️
master/buildbot/configurators/__init__.py	91.66% <0%> (ø)
master/buildbot/configurators/janitor.py	95.74% <0%> (ø)
master/buildbot/monkeypatches/twisted9127.py	36.36% <0%> (ø)
master/buildbot/interfaces.py	98.93% <0%> (+0.01%)	⬆️
master/buildbot/www/auth.py	95.61% <0%> (+0.24%)	⬆️
master/buildbot/config.py	98.68% <0%> (+0.27%)	⬆️
master/buildbot/monkeypatches/__init__.py	87.09% <0%> (+1.38%)	⬆️
master/buildbot/steps/mswin.py	100% <0%> (+3.5%)	⬆️

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[tardyp]

could you replace easy_install with pip ?
there is a need for a pip install -U pip in the first place

[tardyp]

thanks!