Fix int/2 generator

The issue was that the maximum value picked for the generator was
the highest between SampleSize (which is potentially very big)
and Diff (which is the real maximum we don't want to cross).
Instead we now pick the lowest, ensuring that we won't generate
a value bigger than Diff.

Tests suggested by @krestenkrab.
changes the int(L,M) selection range to range across the entire given range regardless of current sample size,
ameliorating common scenarios under which the sample size never gets large enough to cover a representative
sample of the spectrum
Merge branch 'full_spectrum_int_ranges' of https://github.com/Cloven/triq into full_spectrum_int_ranges