various python3 fixes and import organizations, remove unneeded python module

reorganized the imports so they are all at the top of the files, made it so that all the imports correctly import for python 3 (haven't tested python 2 yet, but it should work...), made it so that the KDB4_SALSA20_IV is correctly created in python3 and python 2 by using unhexlify rather then... decode('hex') or whatever it was, removed the pureSalsa20.py file as we are already using pycrypto and that has salsa20?