Allow the use of data stored in STON format in a template.

[demarey]

It is useful, for example, to build a menu by using mustache sections facilities.
Also define a trait to reuse data setup for testing

[demarey]

WARNING: this PR depends on #9

[noha]

Christophe we should have a discussion. I don't want to frustrate you but there is so many things questionable I'm not fine with.
Introducing a Trait is raising complexity. Doing that for the potential usefullness of having memory filesystem. It is a static site generator. So we have a disk that we can use and have no side case that only works in memory filesystem.
The dataPath I don't get either. So we should talk

[demarey]

Introducing a Trait is raising complexity.

Traits are now part of the Pharo core and are just a way to reuse pieces of code. Where do you see complexity?
Also it is only used in tests. It allows faster write of tests and, yes using memory filesystem in tests is important to do not pollute shared resources (disk file system) and get faster runs of tests. If you really do not like it, it can be transformed into a subclass of TestCase.

Yes, we can talk so you can see what data the user would want to use in templates (ex: a description of a menu hierarchy that could be transformed by Mustache).