Improve compatibility with Cygwin and python 3 now tested on Windows CPython 2.7.13 and Cygwin Python 2.7.14 as well as MacOS High Sierra with homebrew Python 2.7.14 and 3.6.3.
- added fixed salt generator
- replace array.array with bytearray
- properly convert bytearray to str in Python2 and 3
- fixed tests to consider results are bytes not str
- moved padding function to encryptor
- added fixed salt generator