Replace ScanRightSeedCount<> with tuple
Replace ScanRightSeedCount<> with tuple

This was a to-do once .NET 3.5 target was dropped.

morelinq/MoreLINQ,ddpruitt/morelinq,fsateler/MoreLINQ,morelinq/MoreLINQ,ddpruitt/morelinq,fsateler/MoreLINQ