Update _continuous_distns.py

fixed bug #4030 simplify scipy.stats.betaprime.cdf.
Update _discrete_distns.py

fixed bug #4028
Update _continuous_distns.py

Final fix of Bug #4030
Update _discrete_distns.py

FInal fix of bug #4028
Revert "Update _discrete_distns.py"

This reverts commit 4e5b1e48fc3516c247015a3da41214b485204f2b.
Revert "Update _continuous_distns.py"

This reverts commit 4817df70ac6af1dd25dc7d775d13a0c460b0462b.
Revert "Update _continuous_distns.py"

This reverts commit 4eee8938cc5593bf856a6ea3c4d652c8604b0c3b.
Revert "Update _discrete_distns.py"

This reverts commit 52dd4c1247d07b0021a6737d4ff541ade83099c5.