add phpunit tests
add minimal function definitions
move static Lazzzy to Container class
move from \Traversable to \Iterator
add "map" method
add "filter" method
add "take" method
extract mockLazyIterator for test purposes
extract provider_all_iterator from test
extract mockIterator for test
add "takeWhile" method
rename static "iterator" to "from"
add "each" method
add "windowed" method