updated README with useful information around usage

Author: dmabry

README.md

@@ -1,2 +1,28 @@
 # flowproxy
 Intelligent Flow Proxy
+
+## Usage
+
+```shell
+Tproxy is used to accept flows and relay them transparently to multiple targets
+
+  -device string
+    	the device the proxy should use (default "eth0")
+  -outfile string
+    	file to write statistics and information to.
+  -port int
+    	the udp port the proxy should use (default 9995)
+  -rate int
+    	sample rate to be used for sending flows along.If 0 all flows will be sent.
+  -target value
+    	Can be passed multiple times in IP:PORT format
+  -verbose
+    	Whether to log every flow received. Warning can be a lot
+```
+
+## Examples
+```shell
+# run flowproxy using transparent proxy listening for udp packets on device en8 and port 9995.
+# Target upstream collector 10.1.1.200 on port 9997 with a sample rate of 4096
+flowproxy tproxy -device en8 -port 9995 -target 10.1.1.200:9997 -rate 4096
+```