Add conda to docs

[ewu63]

Purpose

I added information regarding conda, including installation instructions and a badge to the README. I also fixed some minor formatting issues in the RST files.

Type of change

What types of change is it?
Select the appropriate type(s) that describe this PR

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

There are no code changes.

Checklist

Put an x in the boxes that apply.

• I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

Merging #267 (04e850e) into master (c3782fc) will decrease coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #267      +/-   ##
==========================================
- Coverage   83.65%   83.53%   -0.13%     
==========================================
  Files          22       22              
  Lines        3274     3274              
==========================================
- Hits         2739     2735       -4     
- Misses        535      539       +4     

Impacted Files	Coverage Δ
pyoptsparse/pyOpt_MPI.py	67.64% <0.00%> (-11.77%)	⬇️

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[marcomangano]

Looks good! We can go ahead and ignore the failed test on the TACC image, right?

[ewu63]

Looks good! We can go ahead and ignore the failed test on the TACC image, right?

Yep exactly. Once we have the required reviews I can just merge this.