Experimenting with semantics (Issue #26)

There is a tension between

• Offering a unified semantics
• Experimenting with different variants

See issue 26 for more discussion.

The current approach is to have a module namespace Reactive.Banana.Experimental where different experiments can coexist with the more stable parts of the module hierarchy. The idea is that experimental modules are subject to change; in particular, they are likely to move either up or out in future versions.