Consistency with standard library conventions

[milibopp]

Consistency with standard library conventions

[milibopp]

Concrete changes:

• Iteration over stream events
  • StreamIter → Events.
  • Stream::iter → Stream::events.
• Stream filtering
  • Stream::filter → Stream::filter_just. This is not in IteratorExt, but Sodium has a function filterJust with the same functionality.
  • Stream::filter_with → Stream::filter as in IteratorExt.
  • Provide Stream::filter_map as a shortcut for .map(...).filter_just().
• Accumulation
  • Stream::accumulate → Stream::scan. This method is conceptually very similar to IteratorExt::scan. As a side note RxMarbles also calls this concept scan.
  • The argument should be a binary function instead of a unary function operating on a 2-tuple. This is also more consistent with IteratorExt::scan.