Spelling fix
Pulling from Github.
Added xmax case to discrete PDF normalizing factor for truncated power law and
    stretched exponential.
Set discrete PDF normalizing factor property from the Distribution
class to False, so it won't exist unless explictly created. The method
for calculating it directly from CDFs, which was implemented, only works
    if you have discrete CDFs, which is presently only the case for the
        power law.