We need to use real cross-platform packaging tool

People seems to be interested by the project, we are grown up now, we need to use real packagers tooling.

This is mostly WIP for now, it need to replace our craftsman Makefile by a `_oasis` and its `_tags` which will produce a shiny `setup.ml` with all the feature we can dream.

TODO:
- [x] basic _oasis compiling the lib
- [x] generate the documentation
- [ ] generate test binaries
- [ ] test commands
- [ ] travis integration
- [ ] ocverall integration
- [ ] deploying commands (including opam generation, documentation, Makefile, etc.)