Compact printing in cut

[bkamins]

Currently we have:

julia> cut(1:10, 3)
10-element CategoricalArray{String,1,UInt32}:
 "Q1: [1.0, 4.0)"
 "Q1: [1.0, 4.0)"
 "Q1: [1.0, 4.0)"
 "Q2: [4.0, 6.999999999999999)"
 "Q2: [4.0, 6.999999999999999)"
 "Q2: [4.0, 6.999999999999999)"
 "Q3: [6.999999999999999, 10.0]"
 "Q3: [6.999999999999999, 10.0]"
 "Q3: [6.999999999999999, 10.0]"
 "Q3: [6.999999999999999, 10.0]"

which is not nice. It would be better to use compact printing.

Though we should make sure to correctly do this case:

julia> cut(1:10^-12:1+10^-11, 3)
11-element CategoricalArray{String,1,UInt32}:
 "Q1: [1.0, 1.0000000000033333)"
 "Q1: [1.0, 1.0000000000033333)"
 "Q1: [1.0, 1.0000000000033333)"
 "Q1: [1.0, 1.0000000000033333)"
 "Q2: [1.0000000000033333, 1.0000000000066667)"
 "Q2: [1.0000000000033333, 1.0000000000066667)"
 "Q2: [1.0000000000033333, 1.0000000000066667)"
 "Q3: [1.0000000000066667, 1.00000000001]"
 "Q3: [1.0000000000066667, 1.00000000001]"
 "Q3: [1.0000000000066667, 1.00000000001]"
 "Q3: [1.0000000000066667, 1.00000000001]"

[andreasnoack]

I just hit a similar case hwere the many digits made plotting labels look ugly. What about supporting rounding in the cut(array, ngroups) method instead of just changing the printing? I guess it might be confusing if the string here don't reflect the actual cuts.