use ElementType!R1 instead of typeof(inputRange.front)
Merge pull request #2551 from e10s/patch-1

tweak std.range.tee
std.numreic: added sumOfLogarithms

renamed, and updated

remove CustomFloat support

remove blank line

update comment

update return type

rename sumOfLogs -> sumOfLog2s

update unittest
Merge pull request #2500 from 9il/sum-of-logs

added sumOfLog2s
Implement chunkBy.