Minor improvements to Iterable.scan()
Merge pull request #501 from gdejohn/scan

Minor improvements to Iterable.scan()
add link
add interleave() function
document Iterable.paired
minor
refine size/empty
add corresponding() function
links
sp
ws, etc
add more functions for working with paired streams
reorg source
share impls
define what "any" and "every" mean when there are no elements
plural