Add more editor's syntax support

As suggested by @cobyism for issue #46, it was effectively the check that unable the stylus files to be understood.

After some tests, and observing the structure of the `/vendor/snippets.json` file, it appears to be better to return the good syntax for the file, as snippets.json allows to add syntax-specific snippets and extends syntaxes.

As side-effect, this pull request also correcting issue #40