0xjs README/website docs update

packages/website/md/docs/0xjs/0.0.1/async.md

@@ -0,0 +1,26 @@
+0x.js is a promise-based library. This means that whenever an asynchronous call is required, the library method will return a native Javascript promise. You can therefore choose between using `promise` or `async/await` syntax when calling our async methods.
+
+_Async/await syntax (recommended):_
+
+```javascript
+try {
+    var availableAddresses = await zeroEx.getAvailableAddressesAsync();
+} catch (error) {
+    console.log('Caught error: ', error);
+}
+```
+
+_Promise syntax:_
+
+```javascript
+zeroEx
+    .getAvailableAddressesAsync()
+    .then(function(availableAddresses) {
+        console.log(availableAddresses);
+    })
+    .catch(function(error) {
+        console.log('Caught error: ', error);
+    });
+```
+
+As is the convention with promise-based libraries, if an error occurs, it is thrown. It is the callers responsibility to catch thrown errors and to handle them appropriately.