Improve warning for React.createClass (facebook#9781)

* Improve warning for `React.createClass`

**what is the change?:**
- Explain that this will be removed in v16.0 specifically
- Mention the version number for the drop-in replacement module.
- Link to docs in the blog post about how to migrate

**why make this change?:**
We want to make our deprecation warnings more clear and helpful.

**test plan:**
Visual inspection and `yarn test`

**issue:**
facebook#9398

* Widen range of recommended replacement module versions

**what is the change?:**
Instead of recommending specific versions of 'prop-types' and
'create-react-class' we ask folks to use the latest available 15.* version.

**why make this change?:**
The latest version of those plugins, within the 15 version, is the most likely
to be stable. For example, we know that 'react-create-class' is broken for AMD
builds at the current latest version, so once we release a fix then the
recommended version will change.

**test plan:**
Visual inspection
Also fixed some tests.

* Fix typos and things

**what is the change?:**
- `migrade` -> `migrate`
- `15.* prop-types package` -> `v15.* prop-types package`

**why make this change?:**
Correctness

**test plan:**
`yarn test` and visual inspection

Author: flarnie

src/isomorphic/React.js

@@ -112,8 +112,7 @@ if (__DEV__) {
           didWarnPropTypesDeprecated,
           'Accessing PropTypes via the main React package is deprecated,' +
             ' and will be removed in  React v16.0.' +
-            ' Use the prop-types package from npm instead.' +
-            ' Version 15.5.10 provides a drop-in replacement.' +
+            ' Use the latest available v15.* prop-types package from npm instead.' +
             ' For info on usage, compatibility, migration and more, see ' +
             'https://fb.me/prop-types-docs',
         );
@@ -126,10 +125,12 @@ if (__DEV__) {
       get: function() {
         lowPriorityWarning(
           warnedForCreateClass,
-          'React.createClass is no longer supported. Use a plain JavaScript ' +
-            "class instead. If you're not yet ready to migrate, " +
-            'create-react-class is available on npm as a temporary, ' +
-            'drop-in replacement.',
+          'Accessing createClass via the main React package is deprecated,' +
+            ' and will be removed in React v16.0.' +
+            " Use a plain JavaScript class instead. If you're not yet " +
+            'ready to migrate, create-react-class v15.* is available ' +
+            'on npm as a temporary, drop-in replacement. ' +
+            'For more info see https://fb.me/react-create-class',
         );
         warnedForCreateClass = true;
         return createReactClass;

src/isomorphic/__tests__/React-test.js

@@ -45,10 +45,12 @@ describe('React', () => {
     expect(createClass).not.toBe(undefined);
     expect(console.warn.calls.count()).toBe(1);
     expect(console.warn.calls.argsFor(0)[0]).toContain(
-      'React.createClass is no longer supported. Use a plain ' +
-        "JavaScript class instead. If you're not yet ready to migrate, " +
-        'create-react-class is available on npm as a temporary, ' +
-        'drop-in replacement.',
+      'Warning: Accessing createClass via the main React package is ' +
+        'deprecated, and will be removed in React v16.0. ' +
+        "Use a plain JavaScript class instead. If you're not yet ready " +
+        'to migrate, create-react-class v15.* is available on npm as ' +
+        'a temporary, drop-in replacement. ' +
+        'For more info see https://fb.me/react-create-class',
     );
   });
 
@@ -61,10 +63,9 @@ describe('React', () => {
     expect(console.warn.calls.argsFor(0)[0]).toContain(
       'Warning: Accessing PropTypes via the main React package is ' +
         'deprecated, and will be removed in  React v16.0. ' +
-        'Use the prop-types package from npm instead. ' +
-        'Version 15.5.10 provides a drop-in replacement. ' +
-        'For info on usage, compatibility, migration and more, ' +
-        'see https://fb.me/prop-types-docs',
+        'Use the latest available v15.* prop-types package from ' +
+        'npm instead. For info on usage, compatibility, migration ' +
+        'and more, see https://fb.me/prop-types-docs',
     );
   });
 });