Tweak the C environment, add $CFLAGS & $CXXFLAGS
fix path to static libs built as deps for libmutton
Added liblua.a - this is non-standard, e.g. not from brew
Added post_host for `eunit` test to verify port_driver will load.

Thanks to Dave Cottlehuber [1] for helping out with getting our Erlang
binding to that sheep meat library.

[1] https://github.com/dch
link to the dynamic libmutton
fixed the erl_driver.h mismatch error, the structure of the struct was a little off, coppied one from another project
Moving to a `plain` port without rebar/etc.
Defined external program that we will delegate to.
Initial `plain` port communication established.
Implemented `plain` port calls to libmutton.