Call wrapped subscribe directly
Remove extra subscribeInternal reference from Source
Implement Bus with prototypes
Dispatchers with prototypes
Optimise Bacon.later, Bacon.never and Bacon.once
Do not bind push to dispatcher instances
Do not bind push to Bus instances
Use .call instead of .apply when calling with one argument
Make Bacon.when and UpdateBarrier.intransaction optimisable by V8

These are hit quite often, so it makes sense to allow optimisations by
avoiding try-catch/try-finally and slicing arguments.
Compile browser performance tests with source maps
remove duplication
remove subscribeInternal as unnecessary indirection