Macroize TransfigureTo implicits

Use a (paradise) macro to generate TransfigureTo implicits, with a view towards making transfigure usable for taller towers of monads (without writing insane amounts of code).

This does not yet provide any directly usable features (and it means removing the join functionality), but it proves that the approach can work (at least as far as passing the existing tests), so I figured it was worth checking in and seeing what you think before I dive into the other half of the implementation. (I'm lmm, we spoke a little about this on IRC).

I'm not very familiar with SBT, so there's probably a more elegant way to specify that the build should use the macro paradise plugin.