update readme to document immediate parameter

README.md

@@ -216,8 +216,9 @@ var handle = client.execute({
             program: "data('cpu.utilization').mean().publish()",
             start: Date.now() - 60000,
             stop: Date.now() + 60000,
-            resolution: 10000});
-
+            resolution: 10000,
+            immediate: false});
+
 handle.stream(function(err, data) { console.log(data); });
 ```
 
@@ -228,11 +229,12 @@ Please note that a token created via the REST API is necessary to use this API.
 Parameters to the execute method are as follows :
 
 + **program** (string) - Required field. The signalflow to be run.
-+ **start** (int | string) - A milliseconds since epoch number or a string representing a relative time : e.g. -1h. Defaults to now.  
-+ **end**  (int | string) - A milliseconds since epoch number or a string representing a relative time : e.g. -30m.  Defaults to infinity.
-+ **resolution** (int) - The interval across which to calculate, in 1000 millisecond intervals.  Defaults to 1000. 
++ **start** (int | string) - A milliseconds since epoch number or a string representing a relative time : e.g. -1h. Defaults to now.
++ **stop**  (int | string) - A milliseconds since epoch number or a string representing a relative time : e.g. -30m.  Defaults to infinity.
++ **resolution** (int) - The interval across which to calculate, in 1000 millisecond intervals.  Defaults to 1000.
 + **maxDelay** (int) - The maximum time to wait for a datapoint to arrive, in 10000 millisecond intervals.  Defaults to dynamic.
 + **bigNumber** (boolean) - True if returned values require precision beyond MAX_SAFE_INTEGER.  Returns all values in data messages as bignumber objects as per https://www.npmjs.com/package/bignumber.js  Defaults to false.
++ **immediate** (boolean) - Whether to adjust the stop timestamp so that the computation doesn't wait for future data to be available.
 
 #### Computation Objects