Add options description to the README

README.md

@@ -10,6 +10,15 @@ Example which parses nmap XML and outputs Markdown tables
 python nmap2md.py /path/to/file/test.xml -c protocol,port,service,product,version --hs 4
 ```
 
+* `-c` is used to define columns (their order will reflect end result)
+    * Supported columns:
+    * `port`
+    * `protocol`
+    * `service`
+    * `product`
+    * `version`
+* `--hs` is **h**eader **s**ize. Size variations: from 1 to 6.
+
 ## Output example
 
 #### 74.207.244.221