add support to ip range and limit remote to ip address only

1. proxifier would pass ip address to proxy with "Resolve hostnames
   through proxy" turned off
2. allowing ip range like "192.168.0.0" would shorten the configuration
   file
remove PAC server and shadowsocks/cow as parent proxy
remove test files
ignore "cow" instead of "cow-proxy"
remove builtin sites (which are domains)
save blocked sites to SiteStat only
build script: use gnu-sed and build for darwin amd64 only