Update TransactionController README (#8526)

app/scripts/controllers/transactions/README.md

@@ -40,7 +40,8 @@ txMeta = {
     "gas": "0x7b0c",
     "nonce": "0x0"
   },
-  "history": [{ //debug
+  "history": [
+    { // debug information
       "id": 2828415030114568,
       "time": 1524094064821,
       "status": "unapproved",
@@ -52,13 +53,12 @@ txMeta = {
         "value": "0x0"
       }
     },
-          [
+    [{
-            {
       "op": "add",
       "path": "/txParams/gasPrice",
       "value": "0x3b9aca00"
-            },
+    }]
-            ...], // I've removed most of history for this
+  ], // I've removed most of history for this
   "origin": "MetaMask", //debug
   "nonceDetails": {
     "params": {