README: updated tx-from-calls usage example

.gitignore

@@ -2,3 +2,5 @@
 /membership
 /result
 *.wasm
+*.zk.bin
+*.call

README.md

@@ -126,10 +126,17 @@ create the actual transaction and attach the `fee` call to pay any
 necessary execution fees on-chain.
 
 ```shell
-$ ./drk tx-from-calls < ../smart-contract/register.call | ./drk attach-fee > register.tx
+$ ./drk tx-from-calls < ../smart-contract/register.call > register.tx
 $ ./drk broadcast < register.tx
 ```
 
+We can create a `deregister` call using the same steps:
+
+```shell
+$ ./membership deregister {CONTRACT_ID} {IDENTITY_SECRET_KEY} > deregister.call
+$ ./drk tx-from-calls < ../smart-contract/deregister.call > deregister.tx
+$ ./drk broadcast < deregister.tx
+```
 
 ## License