Update txRunner.js

src/app/execution/txRunner.js

@@ -11,7 +11,7 @@ function TxRunner (vmaccounts, opts) {
   this.runAsync = true
   if (executionContext.isVM()) {
     this.blockNumber = 1150000 // The VM is running in Homestead mode, which started at this block.
-    this.runAsync = false
+    this.runAsync = false // We have to run like this cause the VM Event Manager does not support running multiple txs at the same time.
   }
   this.pendingTxs = {}
   this.vmaccounts = vmaccounts