[#2125] Update to pelican build system

Problem
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Styleguide pages was using an outdated hyde build system... which fails when trying to pull deps again.


Changes
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Swich code to pelican which is maintained and has tests.

Beside renaming and a few small changes in templates the migration was lean as pelican is also using RST and jinja2.

Hosting was moved from Dremahost to GitHub pages. This is a big improvement  since now anyone can push the changes. ... Pushing still does not work on Windows due to this bug https://github.com/davisp/ghp-import/pull/23 ... but hope the bug will be fixed soon.

build system was also update to latest paver.sh this is why the changes.

styleguide.chevah.com DNS entry was changes as a CNAME for chevah.github.io


How to test
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reviewers: @alibotean @dumol 
depends-on: #11 

This branch is based on #11 and this is why the diff is bigger... I will ask for review once parent is merged.

Check README... but this is just to let you know about the change.

This review also needs to wait for DNS to be updated.

Thanks!

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