Add • compose operator and failing lens test

That passes in https://github.com/maxpow4h/swiftz/commit/fd76c15a5f12412640ad102ba700cd4d600b069c .
My old code:
```
Party.lpartyHost().modify(party, { User.luserName().set($0, "Max") })
```
is now equivalent to:
```
(Party.lpartyHost() • User.luserName()).set(party, "Max")
```
:smile: :boom: