enif_get_string can return < 1 when it copies less than the buffer size
you pass into it, that'd result in a non-zero (aka true) test when in fact
it's a problem if the argument isn't passed completely (however unlikely
that is).

enif_alloc_env() requires that later you enif_free_env() which I wasn't doing,
this seems to keep memory steady in test runs.
Shared libs and files linking to them must be copied into our priv
dir so that at runtime we can find the correct files.
Merge branch 'gsb-async-nifs3' of github.com:basho-labs/wterl into gsb-async-nifs3