docs(operators): add documentation for sample

Close #95

Author: ashwin-sureshkumar

src/operator-docs/filtering/sample.ts

@@ -1,6 +1,56 @@
 import { OperatorDoc } from '../operator.model';
 
 export const sample: OperatorDoc = {
-  'name': 'sample',
-  'operatorType': 'filtering'
+  name: 'sample',
+  operatorType: 'filtering',
+  signature: `public sample(notifier: Observable<any>): Observable<T>`,
+  parameters: [
+    {
+      name: 'notifier',
+      type: 'Observable<any>',
+      attribute: '',
+      description: 'The Observable to use for sampling the source Observable.'
+    }
+  ],
+  marbleUrl: 'http://reactivex.io/rxjs/img/sample.png',
+  shortDescription: {
+    description:
+      'Emits the most recently emitted value from the source Observable whenever another Observable, the notifier, emits.',
+    extras: [
+      {
+        type: 'Tip',
+        text: `It's like sampleTime, but samples whenever the notifier Observable emits something.`
+      }
+    ]
+  },
+  walkthrough: {
+    description: `
+      <p>
+       Whenever the notifier Observable emits a value or completes,
+       sample looks at the source Observable and emits whichever value it has most recently emitted since the previous sampling,
+       unless the source has not emitted anything since the previous sampling.
+      </p>
+      <p>
+       The notifier is subscribed to as soon as the output Observable is subscribed.
+      </p>
+    `
+  },
+  examples: [
+    {
+      name: 'On every click, sample the value from source every 2 seconds',
+      code: `
+      //emit value every 1s
+      const source = Rx.Observable.interval(1000);
+      //sample last emitted value from source every 2s
+      const example = source.sample(Rx.Observable.interval(2000));
+      //output: 2..4..6..8..
+      const subscribe = example.subscribe(val => console.log(val));
+      `,
+      externalLink: {
+        platform: 'JSBin',
+        url: 'http://jsbin.com/gemebopifu/1/embed?js,console'
+      }
+    }
+  ],
+  relatedOperators: ['audit', 'debounce', 'sampleTime', 'throttle']
 };