Feature/8 return a promise (#5) (#6)

* Resolve "Pass Entire JSON String to the user"

* Add a promise function

* Adjust documentation

* Fix ci issues

* Fix ci issues 2

Co-authored-by: Ethan Lane <ethan.lane@influentialsoftware.com>

Co-authored-by: Ethan Lane <ethan.lane@influentialsoftware.com>

readme.md

@@ -12,13 +12,20 @@ $ npm install --save random-bunny
 ## Usage
 
 ```js
-const randomBunny = require('random-bunny');
+const { randomBunny } = require('random-bunny');
 
 randomBunny('rabbits', 'new', res => {
     console.log(res.title + ": " + res.url);
 });
 ```
 
+```js
+const { promise } = require('random-bunny');
+
+promise('rabbits', 'new').then((res) => {
+    console.log(res.title);
+});
+```
 
 ## API
 
@@ -37,6 +44,12 @@ The json string which gets returned consists of:
 - ups
 - url
 
+### `promise()`
+
+Returns a `json string` for a random post in a `promise`. Accepts 2 arguments: `subreddit`, `sortby` ('new', 'hot', 'top').
+
+The json string returned in the promise consists of the same above.
+
 ## Notes
 
 * Node 4 or newer.