Support for systems without <endian.h>

[tnovotny]

Many operating systems do not have an <endian.h> file. This is used in stream_helpers.hpp. Consider adding a portable <endian.h> file

[WhiZTiM]

@tnovotny. Awesome! Thanks! I will do it over this weekend (and other changes/improvements). However, if you could make a pull request for this applying this endian portability changes, I will happily merge right away!

-Timothy