Add some missing words to the creating a theme page

Update t-rex.tileserver.ch

update zola version on deployment docs

use travis "minimal" vm in the documentation

If not specified, Travis use a system with ruby, which we don't need. We can use the "minimal" one instead.

Closes #530

Closes #636

v.0.6.0

Allow default base-path command line option to be set for building and serving.

Close #633

Split sitemap when it is getting too big

To ensure we will get the right `content`
directory.
Fix #629

Fix minor documentation quirks in templates/overview

Fix #613

Add maxdeviant.com to examples

adding back default in rebuild

Fix #620

use nix-shell to build on nixos

Fix #616. Add brief documentation for how to use it.

fix minor typo in doc template