WIP on alternative technique to fixing #123
Closes #123 for good

Ping @pstutz: You should be able to compile `signal-collect` with the
miniboxing plugin by adding:
```
scalacOptions += "-P:minibox:hijack
```
to your `build.sbt` file. This way, all `@specialized` annotations
will be redirected to `@miniboxed` instead. I will be looking into
the reference warnings soon and I have a couple more bugs when using
`-P:minibox:mark-all` (which triggers all type parameters to be
annotated automatically): #121, #123 and #125. Let me know how if
you encounter any issues! Thx!