Update README.md

Author: mcabbott

README.md

@@ -33,5 +33,7 @@ As will any features which migrate to Flux itself.
 
 ## Current Features
 
-* Layers `Split` and `Join`
-* A more advanced `train!`
+* Layers [`Split` and `Join`](https://github.com/FluxML/Fluxperimental.jl/blob/master/src/split_join.jl)
+* More advanced [`train!` function](https://github.com/FluxML/Fluxperimental.jl/blob/master/src/train.jl)
+* Macro for [making custom layers](https://github.com/FluxML/Fluxperimental.jl/blob/master/src/compact.jl) quickly
+* Experimental [`apply(c::Chain, x)`](https://github.com/FluxML/Fluxperimental.jl/blob/master/src/chain.jl) interface