Update README.md

Author: topofocus

README.md

@@ -39,7 +39,9 @@ puts ib.recieved[:OrderStatus].to_human
 # => ["<OrderState: Submitted #17/1528367295 from 2000 filled 0.0/100.0 at 0.0/0.0 why_held >"]
 
 ```
+## Minimal TWS-Version
 
+`ib-api` is tested via the _stable ib-Gateway_ (Version 9.72) 
 
 ## Tests
 
@@ -54,7 +56,6 @@ Integration tests on order-placements are not included. To run the test suite it
 You have to edit `spec/spec.yml` and replace the `:account`-Setting with your own `AccountID`, even if you connect to a single account. 
 
 
-
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/ib-api. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.