Added python-markdown and graphviz dependencies to README
Added python-markdown and graphviz dependencies to README

wyrdmantis/libsnark,wyrdmantis/libsnark,gstew5/libsnark,martindale/libsnark,martindale/libsnark,jl777/libsnark,gstew5/libsnark,jl777/libsnark,jl777/libsnark,gstew5/libsnark,nivertech/libsnark,martindale/libsnark,wyrdmantis/libsnark,nivertech/libsnark,nivertech/libsnark