[DOC] Rearrange badges in README

[tsalo]

Changes proposed in this pull request:

• Add PyPi badge to repo and docs READMEs
• Reorder badges in repo README to go usage --> status info for devs --> serious dev info (e.g., where to talk about code on Gitter)

[KirstieJane]

Looks logical to me ✅

[codecov]

Codecov Report

Merging #118 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #118   +/-   ##
=======================================
  Coverage   49.72%   49.72%           
=======================================
  Files          32       32           
  Lines        2035     2035           
=======================================
  Hits         1012     1012           
  Misses       1023     1023

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[emdupre]

LGTM ! Thanks, @tsalo !