Update to Documenter 0.20

[mortenpi]

Not sure if this will actually work.

Due to upcoming breaking changes in Documenter. This makes sure that the doc builds do not start failing when 0.20 lands in METADATA. See this thread on Discourse for more information.

Ref: JuliaDocs/Documenter.jl#861

[codecov-io]

Codecov Report

Merging #1217 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1217   +/-   ##
=======================================
  Coverage   73.13%   73.13%           
=======================================
  Files          35       35           
  Lines        4042     4042           
=======================================
  Hits         2956     2956           
  Misses       1086     1086

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[mortenpi]

Ok, it didn't work. I might get back to this in a few days.

[tlnagy]

Thanks for the PR, did you get a chance to look into this more?

[mortenpi]

Apologies for not getting back to this earlier. So, instead of capping Documenter to 0.19, I've simply updated make.jl so that it would work with the latest version. I also switched to using docs/Project.toml to list the docs-only dependencies.

If Travis passes, it should be good to go. It is also using a build stage now, which means that documentation build failures should also fail Travis now by failing the "Documentation" build stage.

[mortenpi]

I forgot about this before -- this also makes another change. Currently, the docs from master end up under the http://gadflyjl.org/latest/ URL, but with this PR they start deploying to http://gadflyjl.org/dev/. This is the new recommended default but it can be changed.

If you are OK with changing the URL, I can update the links in the README right away. If not, I'll add a keyword to deploydocs to keep it at latest/.

The latest tagged version will still be available from stable/, so no change to that.

[bjarthur]

i'm find with dev/ instead of latest/. make the change to the REAME and i'll merge.

[mortenpi]

Done.

[bjarthur]

thanks!