Merge pull request #494 from aoberoi/migration-guide-docs

adds link to migration guide onto landing pages

README.md

@@ -10,6 +10,10 @@ So you want to build a Slack app with Node.js? We've got you covered. This packa
 building Slack apps ridiculously easy. It helps you build on all aspects of the Slack platform, from dropping
 notifications in channels to fully interactive bots.
 
+**Upgrading from version 3?** The
+[migration guide](https://github.com/slackapi/node-slack-sdk/wiki/Migration-Guide-for-v4) has all the information you
+need to bring your app up to speed.
+
 ## Requirements
 
 This package supports Node v6 and higher. It's highly recommended to use

docs/index.md

@@ -51,6 +51,10 @@ through building your first Slack app using Node.js.
 that explains and compares the options. If you're still not sure,
 [reach out for help](#getting-help) and our community can guide you.
 
+**Upgrading from version 3?** The
+[migration guide](https://github.com/slackapi/node-slack-sdk/wiki/Migration-Guide-for-v4) has all the information you
+need to bring your app up to speed
+
 ---
 
 You'll notice that some of the API tools are not included in the `@slack/client` package.

migration_guide_v4.md

@@ -214,6 +214,39 @@ between events in the `v3.x` series and events in the `v4.x` series.
    - `unfurlLinks` => `unfurl_links`
    - `unfurlMedia` => `unfurl_media`
 
+## CLIENT_EVENTS, RTM_EVENTS, RTM_MESSAGE_SUBTYPES
+
+These constants have been removed. We recommend using simple strings for event names. The values that were in
+`CLIENT_EVENTS` have been migrated according to the [events table above](#events). The `RTM_EVENTS` dictionary isn't
+necessary, just directly subscribe to the event name as a string.
+
+**Before:**
+```javascript
+rtm.on(CLIENT_EVENTS.RTM.AUTHENTICATED, (connectionData) => {
+  console.log('RTMClient authenticated');
+});
+
+rtm.on(RTM_EVENTS.MESSAGE, (event) => {
+  console.log(`Incoming message: ${event.ts}`);
+})
+```
+
+**After:**
+```javascript
+rtm.on('authenticated', (connectionData) => {
+  console.log('RTMClient authenticated');
+});
+
+rtm.on('message', (event) => {
+  console.log(`Incoming message: ${event.ts}`);
+})
+```
+
+## RETRY_POLICIES
+
+The names of these policies have slightly changed for more consistency with our style guide. The dictionary of policies
+is now exported under the name `retryPolicies`. See `src/retry-policies.ts` for details.
+
 ## Proxy Support with `agent`
 
 In order to pass outgoing requests from `WebClient` or `RTMClient` through an HTTP proxy, you'll first need to install