This CL changes the function signature from StDev to StdDev to match the other StandardXxx functions.
Additionally, this PR fixes the comments that don't start with the correct name
and changes +=1 to ++ by recommendation from golint
Lists should be separated out into their own block (see the reflect package).
It was decided in code review that Quantile and Percentile are confusing
so it was decided to change it to Quantile and CDF