Added conversion from RioStream to IOStream.

Signed-off-by: Timo Kinnunen <timo.kinnunen@gmail.com>
Fixed immutable Set being empty  when constructed from an iterated
Collection. Unified construction of mutable HashSet to same.

Signed-off-by: Timo Kinnunen <timo.kinnunen@gmail.com>
Fixed bad performance with large group set operations.

Signed-off-by: Timo Kinnunen <timo.kinnunen@gmail.com>
Added vararg-less versions of methods for better IDE use. Whitespace
changes and general cleanup.

Signed-off-by: Timo Kinnunen <timo.kinnunen@gmail.com>
Added example comparison of computeIfAbsent with IOException.

Signed-off-by: Timo Kinnunen <timo.kinnunen@gmail.com>
Added toMap convenience method with key and value mappers.

Signed-off-by: Timo Kinnunen <timo.kinnunen@gmail.com>