Initial range--test with large bin-by-bin variations

[gerbaudo]

In the previous FBU implementation, we defined an initial hyperbox with some range for each bin, i.e. N_bin intervals being sampled.
Now with pymc we are passing in just two values, for example lower and upper:

     DiscreteUniform('truth', lower=50000, upper=150000, doc='truth', size=nreco)

Do we need to define N intervals? can we afford to just define one interval, or is this going to be an issue when the bin content varies by orders of magnitude?
The actual first thing to do is to write a test with a steeply falling distribution.