update README

README.md

@@ -1,2 +1,42 @@
 # gdns
 a dns proxy server write by go
+
+gdns much like dnsmasq or chinadns, but it can run on windows.
+
+Features
+========
+
+support different domains use different upstream servers
+
+support contact to the upstream server by tcp or udp
+
+support blacklist list to block the fake ip
+
+Install
+=======
+
+    # get the depended library
+    go get github.com/miekg/dns
+    go get github.com/vharitonsky/iniflags
+    
+    git clone https://github.com/fangdingjun/gdns
+    cd gdns
+    go build
+    
+    # generate a sample config file
+    ./gdns -dumpflags > dns.ini
+    
+    # edit the dns.ini
+    sudo ./gdns -config dns.ini
+    
+    # test it
+    dig @localhost twitter.com
+    
+Arguments
+===========
+
+use `gdns -h` to show the command line arguments.
+
+all arguments can specialed in config file or in command line.
+
+this is a sample file in the config_sample directory.