Won't run on Mac OS

[renepickhardt]

when running make I get:

....
./types.h:4:10: fatal error: 'openssl/sha.h' file not found
#include <openssl/sha.h>
         ^~~~~~~~~~~~~~~
1 error generated.
make: *** [iterate.o] Error 1

according to: https://www.anintegratedworld.com/mac-osx-fatal-error-opensslsha-h-file-not-found you can install openssl with brew install openssl (which I already had) but then you need to create the symlink like:

> cd /usr/local/include 
> ln -s ../opt/openssl/include/openssl .

not sure if the readme should updated for mac users

[elichai]

I think the best solution is to remove openssl as a dependency and just directly implement sha256 here (200-300 lines of code), and there are a bunch of C public domain implementations out there