Move installation instructions

[ml-evs]

As discussed, closes #136

I've got a "task" working for auto-tagging branches when invoke setver is called, though I think this will mess things up as commits inside PRs will be tagged... unless we are very careful with this I think we need a better automated solution (presumably some kind of bot).

This does mean that the instructions in this PR are incorrect unless we keep manually moving the latest tag to the whatever the current release tag is called.

[codecov]

Codecov Report

Merging #156 into master will not change coverage.
The diff coverage is 57.89%.

@@           Coverage Diff           @@
##           master     #156   +/-   ##
=======================================
  Coverage   85.09%   85.09%           
=======================================
  Files          39       39           
  Lines        1845     1845           
=======================================
  Hits         1570     1570           
  Misses        275      275

Flag	Coverage Δ
#unittests	85.09% <57.89%> (ø)	⬆️

Impacted Files	Coverage Δ
optimade/server/routers/info.py	96.29% <ø> (ø)	⬆️
optimade/server/routers/index_info.py	100% <ø> (ø)	⬆️
optimade/validator/validator.py	62.33% <0%> (ø)	⬆️
optimade/server/main.py	78.57% <53.84%> (ø)	⬆️
optimade/server/main_index.py	76.74% <55.55%> (ø)	⬆️
optimade/server/exception_handlers.py	73.07% <60%> (ø)	⬆️
optimade/server/routers/utils.py	83.07% <70%> (ø)	⬆️
... and 2 more

---

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[CasperWA]

Thanks for this @ml-evs
I am not sure the auto-generating latest tag is a good idea - or rather, it seems too complicated compared to just have master be the latest and if one wants a specific version they can install that tagged version?

Or what did you have in mind? :)

Also - are there any changes going from CONTRIBUTING to INSTALL?

[CasperWA]

I don't think there is a need to create the latest tag - it will naturally be master, which is also the default branch.

[ml-evs]

If that's how we're intending to use master then that's fine, though major releases will invovle some large PRs... or just using a different branch of course.

[CasperWA]

Yeah. I think we should use the recommendation that users pin to a specific version, since master will always be the latest version, and therefore may also introduce backwards-incompatible changes. Right? Or simply use the same dependency scheme we have employed, i.e. optimade~=0.3.3 to keep to the 0.3.x versions, or optimade~=0.3 to keep to the 0.x versions. This will of course mean we should keep publishing to PyPI, but I don't see a problem with that?

[ml-evs]

Also - are there any changes going from CONTRIBUTING to INSTALL?

No changes!

[CasperWA]

This is looking good for me - thanks @ml-evs !

(I found an extra white-space, I just removed it in the suggested change).

[ml-evs]

Cheers @CasperWA