Update bigpicture.rst (spelling) (ThreeMammals#994)

fixed 2 spelling/grammar mistakes.

docs/introduction/bigpicture.rst

@@ -15,11 +15,11 @@ it reaches a request builder middleware where it creates a HttpRequestMessage ob
 used to make a request to a downstream service. The middleware that makes the request is 
 the last thing in the Ocelot pipeline. It does not call the next middleware. 
 The response from the downstream service is stored in a per request scoped repository 
-and retrived as the requests goes back up the Ocelot pipeline. There is a piece of middleware 
+and retrieved as the requests goes back up the Ocelot pipeline. There is a piece of middleware 
 that maps the HttpResponseMessage onto the HttpResponse object and that is returned to the client.
 That is basically it with a bunch of other features.
 
-The following are configuration that you use when deploying Ocelot.
+The following are configurations that you use when deploying Ocelot.
 
 Basic Implementation
 ^^^^^^^^^^^^^^^^^^^^