Printing StackOverflowError

If one implements custom `AbstractMeasure` and not override any printing methods this method leads to an error:
https://github.com/cscherrer/MeasureBase.jl/blob/master/src/utils.jl#L3

That is most likely because `pprint` falls back to `show` at some point.

Replicate in REPL:
```julia
julia> using MeasureBase: AbstractMeasure
julia> struct A <: AbstractMeasure end
julia> A()
Error showing value of type A:
ERROR: StackOverflowError:
```

Few ways to address it, not sure which one you prefer.