angulillos v0.5.0

Several breaking changes here, but mostly about names.

1. We dropped Optional<Stream<X>> in favor of just Stream<X>. An empty stream signals the equivalent of none before. See #40
2. We are using E as a suffix for methods related with edges like outE, inE.
3. The names for arities have changed. See #41 and #40. They are defined in TypedEdge.java.

Apart from that, documentation should display better on github.com. The build plugin was also updated.