add code snippets to docs

Author: havenwang

documentation/snippets/activity.md

@@ -0,0 +1,9 @@
+```javascript
+var product = 'The selected product';
+var userEmail = 'thecurrentuser@me.com';
+Breinify.activity({
+    'email': userEmail
+}, 'selectProduct', null, product, false, function () {
+    show('Sent activity "selectProduct" with product "' + product + '".');
+});
+```

documentation/snippets/config.md

@@ -0,0 +1,5 @@
+```javascript
+Breinify.setConfig({
+    apiKey: '23AD-F31F-F324-6666-AC2D-C526-D829-BBC2'
+});
+```

documentation/snippets/lookup.md

@@ -0,0 +1,10 @@
+```javascript
+var userEmail = 'thecurrentuser@me.com';
+Breinify.lookup({
+    'email': userEmail
+}, ['firstname'], false, function (data) {
+    if (Breinify.UTL.isEmpty(data)) {
+        window.alert('Hello ' + data.firstname.result);
+    }
+});
+```