Anchors to titles containing [^a-z1-9] are not fully GitHub/GitBook compatible

[dpordomingo]

from #450 (comment)

Anchors pointing to titles having ., { or } inside, are generated differently by GitBook and GitHub, so when they're used, they don't work in both.

It was assumed GitBook as the preferred way to render our docs, but we should decide if we keep that rule, or if we want to look for a workaround or alternative

exampls:

title	GitBook	GitHub
config.yml	#config-yml	#configyml
source{d} Engine	#source-d-engine	#sourced-engine