Docs, minor clarification.
Docs, minor clarification.

Clarification added that explains that the `Actor#handle` method registers handlers for a given pattern.
TiagoCardoso1983/celluloid,seuros/celluloid,davydovanton/celluloid,kenichi/celluloid,dilumn/celluloid,celluloid/celluloid,jasonm23/celluloid,olleolleolle/celluloid,marshall-lee/celluloid