Adds a tiny delay in the infinite test code

Without it, it is possible to fill the heap, and to crash the target VM.
Merge pull request #205 from skyluc/issue/not-so-infinite

Adds a tiny delay in the infinite test code
Add a document setup and file buffer-based document provider.

This allows the hovers to retrieve the compilation unit, and it is the
way documents are handled elsewhere (sdt.core, JDT, play2).
Adapt to changes in master.
Add an ‘F3’ action to navigate to definition.

Closes #167.