Chore: Clarified pip install instructions

[kenibrewer]

Description

Clarification in documentation that resolves #253 and will better support anonymous installs of pycytominer from users unfamiliar with the syntax of pip install git+ commands.

What is the nature of your change?

• Bug fix (fixes an issue).
• Enhancement (adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• This change requires a documentation update.

Checklist

Please ensure that all boxes are checked before indicating that a pull request is ready for review.

• I have read the CONTRIBUTING.md guidelines.
• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have made corresponding changes to the documentation.
• I have deleted all non-relevant text in this pull request template.

[codecov-commenter]

Codecov Report

Merging #277 (9a5888b) into master (a5ae6c8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #277   +/-   ##
=======================================
  Coverage   95.07%   95.07%           
=======================================
  Files          57       57           
  Lines        3044     3044           
=======================================
  Hits         2894     2894           
  Misses        150      150           

Flag	Coverage Δ
unittests	95.07% <ø> (ø)

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[danodonovan]

This change is preferred by PyPI

The use of git, git+git, and git+http schemes is discouraged. The former two use the Git Protocol, which lacks authentication, and HTTP is insecure due to lack of TLS based encryption.

https://pip.pypa.io/en/stable/topics/vcs-support/

[kenibrewer]

@gwaybio Could I get a review on this PR?

[gwaybio]

We're currently working toward a version 1 release, which will change the instructions in the README. For us to merge a pip install clarification, I think it is worth removing the pip + git install commands in favor of pip alone (also adding reference to pycytominer on conda) and all other references to pycytominer still being in beta.

[kenibrewer]

Superseded by #289