refactor(refresher): allow refresher content customization

Breaking Change:

## Refresher:

- `<ion-refresher>` now takes a child `<ion-refresher-content>`
component.
- Custom refresh content components can now be replaced for Ionic's
default refresher content.
- Properties `pullingIcon`, `pullingText` and `refreshingText` have
been moved to the `<ion-refresher-content>` component.
- `spinner` property has been renamed to `refreshingSpinner` and now
goes on the `<ion-refresher-content>` component.
- `refreshingIcon` property is no longer an input, but instead
`refreshingSpinner` should be used.

Was:

```
<ion-refresher (refresh)="doRefresh($event)"
pullingIcon="arrow-dropdown">
</ion-refresher>
```

Now:

```
<ion-refresher (refresh)="doRefresh($event)">
  <ion-refresher-content
pullingIcon="arrow-dropdown"></ion-refresher-content>
</ion-refresher>
```

ionic/components/refresher/test/basic/index.ts

@@ -0,0 +1,85 @@
+import {App} from 'ionic-angular';
+
+
+@App({
+  templateUrl: 'main.html'
+})
+class E2EApp {
+  items = [];
+
+  constructor() {
+    for (var i = 0; i < 3; i++) {
+      this.items.push( getRandomData() );
+    }
+  }
+
+  doRefresh(refresher) {
+    console.log('Begin async operation');
+
+    getAsyncData().then(newData => {
+      for (var i = 0; i < newData.length; i++) {
+        this.items.unshift( newData[i] );
+      }
+
+      console.log('Finished receiving data, async operation complete');
+      refresher.endRefreshing();
+    });
+  }
+
+  doStart(refresher) {
+    console.log('Refresher, start');
+  }
+
+  doPulling(refresher) {
+    console.log('Pulling', refresher.progress);
+  }
+
+}
+
+function getAsyncData() {
+  // async return mock data
+  return new Promise(resolve => {
+
+    setTimeout(() => {
+      let data = [];
+      for (var i = 0; i < 3; i++) {
+        data.push( getRandomData() );
+      }
+
+      resolve(data);
+    }, 1000);
+
+  });
+}
+
+function getRandomData() {
+  let i = Math.floor( Math.random() * data.length );
+  return data[i];
+}
+
+const data = [
+  'Fast Times at Ridgemont High',
+  'Peggy Sue Got Married',
+  'Raising Arizona',
+  'Moonstruck',
+  'Fire Birds',
+  'Honeymoon in Vegas',
+  'Amos & Andrew',
+  'It Could Happen to You',
+  'Trapped in Paradise',
+  'Leaving Las Vegas',
+  'The Rock',
+  'Con Air',
+  'Face/Off',
+  'City of Angels',
+  'Gone in Sixty Seconds',
+  'The Family Man',
+  'Windtalkers',
+  'Matchstick Men',
+  'National Treasure',
+  'Ghost Rider',
+  'Grindhouse',
+  'Next',
+  'Kick-Ass',
+  'Drive Angry'
+];

ionic/components/refresher/test/basic/main.html

@@ -0,0 +1,21 @@
+<ion-toolbar><ion-title>Pull To Refresh</ion-title></ion-toolbar>
+
+<ion-content>
+
+  <ion-refresher (start)="doStart($event)" (pulling)="doPulling($event)" (refresh)="doRefresh($event)">
+
+    <ion-refresher-content
+      pullingText="Pull to refresh..."
+      refreshingSpinner="bubbles"
+      refreshingText="Refreshing...">
+    </ion-refresher-content>
+
+  </ion-refresher>
+
+  <ion-list>
+    <ion-item *ngFor="#item of items">
+      {{ item }}
+    </ion-item>
+  </ion-list>
+
+</ion-content>