Link to `CaptureConversions$` in `README.md` is invalid.

[metasim]

Line 167 in README.md has a link to the API docs results in a 404. Sorry I couldn't issue a PR; couldn't figure out where the code referenced now lives.

You can see that captured constants are inlined in the code (see [CaptureConversions](http://ochafik.github.io/Scalaxy/Reified/latest/api/index.html#scalaxy.reified.CaptureConversions$)).
They have been converted from runtime value to AST representations amenable for compilation. The resulting AST has no external value dependency (apart from stable paths & methods).