breakpoint-slicer syntax support added. tests to follow

I did some work on converting this to a syntax that supports a [breakpoint-slicer](https://github.com/lolmaus/breakpoint-slicer) style syntax. It is backwards compatible (no breaking changes).

I still need to write the tests for all of this, and will do so very soon. But you'll have to run them as they all fail on Windows as referenced in #2.

I figured I would just open the PR for now so you can have a little inspect of it. :)