Fix a typo and improve wording of docs in a few places

Summary:Docs are looking great these days 😎 -- here's my humble contribution
Closes jestjs#830

Differential Revision: D3089990

fb-gh-sync-id: 78cb08e982fafa318df5e91164c375d6ab9122ff
shipit-source-id: 78cb08e982fafa318df5e91164c375d6ab9122ff

Author: brentvatne

docs/CommonJSTesting.md

@@ -14,10 +14,6 @@ using a different approach.
 What is the problem?
 --------------------
 
-The [example](https://docs.angularjs.org/guide/unit-testing#dependency-injection)
-that Angular documentation uses to justify Dependency Injection is the
-following:
-
 ```javascript
 function doWork() {
   const xhr = new XHR();
@@ -42,7 +38,7 @@ This small example shows two important concepts. We need a way to get a
 reference to `XHR` and a way to provide two implementations: one for the normal
 execution and one for testing.
 
-In this case, the solution to both concepts is to use the global object. It
+In this case, the solution swaps implementations on the global object. It
 works, but it's not ideal for reasons outlined in this article:
 [Brittle Global State & Singletons](http://misko.hevery.com/code-reviewers-guide/flaw-brittle-global-state-singletons/).
 
@@ -60,7 +56,7 @@ function doWork(XHR) {
 }
 ```
 
-It makes it very easy to write a test – you just pass your mocked version as
+It makes it very easy to write a test – you pass your mocked version as
 argument to your function:
 
 ```javascript

docs/Tutorial.md

@@ -27,7 +27,7 @@ function fetchCurrentUser(callback) {
   return $.ajax({
     type: 'GET',
     url: 'http://example.com/currentUser',
-    done: user => callback(parseJSON(user)),
+    success: user => callback(parseJSON(user)),
   });
 }
 
@@ -76,9 +76,9 @@ version of the real module – so we need to tell Jest not to mock the file we
 want to test or else `require('../fetchCurrentUser')` will return a mock.
 
 In our first test, we want to confirm that calling `fetchCurrentUser()`
-properly incurs a call into `$.ajax()` with the parameters we expect. To do
-this, we just call `fetchCurrentUser()` with a dummy callback function, and
-then simply inspect the `$.ajax` mock to verify that it was called with the
+properly invokes `$.ajax()` with the parameters we expect. To do
+this, we call `fetchCurrentUser()` with a dummy callback function, and
+then inspect the `$.ajax` mock to verify that it was called with the
 correct parameters.
 
 Woohoo! We've written our first test. But we're not quite done: We would still