add readme

README.md

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+# TCP Proxy
+----
+
+[![Build Status](https://ci.trj.tw/api/badges/golang/tcp-proxy/status.svg)](https://ci.trj.tw/golang/tcp-proxy)
+
+## Build
+
+### Bin
+```sh
+$ make
+```
+
+### Docker
+```sh
+$ docker build -t tcp-proxy .
+```
+ 
+## Usage
+
+### Config
+```yaml
+# verbose level 0=info, 1=verbose, 2=very verbose
+verbose: 0
+listen:
+    # connect target host and port
+  - target_host: 192.168.1.1
+    target_port: 22
+    # local listen port
+    listen_port: 22000
+
+    # connect target host ip range and port
+  - target_host: 192.168.1.2-5
+    target_port: 22
+    # local listen port start number (with connect to ip range)
+    listen_port: 22010
+
+    # connect target host with domain name and port
+  - target_host: domain.name
+    target_port: 80
+    listen_port: 22100
+```
+
+### Run
+```sh
+$ tcp-proxy -f /path/to/config.yml
+```