Docs: Add detail to README

README.md

@@ -2,3 +2,62 @@ async-done
 ==========
 
 Manage callback, promise, and stream completion
+
+Will run call the executor function on `nextTick`. This will cause all functions to be async.
+
+## Usage
+
+### Successful completion
+
+```js
+var asyncDone = require('async-done');
+
+asyncDone(function(done){
+  // do async things
+  done();
+}, function(err){
+  // err will be undefined if done callback wasn't passed an error
+});
+```
+
+### Failed completion
+
+```js
+var asyncDone = require('async-done');
+
+asyncDone(function(done){
+  // do async things
+  done(new Error('Some Error Occurred'));
+}, function(err){
+  // err will be the error passed to done callback
+});
+```
+
+## API
+
+### `asyncDone(executor, onComplete)` : Function
+
+Takes a function to execute (`executor`) and a function to call on completion (`onComplete`).
+
+#### `executor([done])` : Function
+
+Optionally takes a callback to call when async tasks are complete.
+
+If a `Stream` (or any instance of `EventEmitter`) or `Promise` is returned from the `executor` function, they will be used to wire up the async resolution.
+
+`Streams` (or any instance of `EventEmitter`) will be wrapped in a domain for error management. The `end` and `close` events will be used to resolve successfully.
+
+`Promises` will be listened for on the `then` method. They will use the `onFulfilled` to resolve successfully or the `onRejected` methods to resolve with an error.
+
+#### `onComplete(err)` : Function
+
+The `onComplete` method will receive an error as its only argument if an error occurred in the execution of the `executor` function.  This includes:
+
+* A thrown error
+* An error passed to a `done` callback
+* An `error` event emitted on a returned `Stream` or `EventEmitter`
+* A rejection of a returned `Promise`
+
+## License
+
+MIT