feat(HomeTabFragment): switch timeline when triple clicking

Closes #83. When clicking the HomeTab and the timeline is already scrolled up, the timeline is cycled.

mastodon/src/main/java/org/joinmastodon/android/fragments/HomeTabFragment.java

@@ -477,6 +477,11 @@ public class HomeTabFragment extends MastodonToolbarFragment implements Scrollab
 
 	@Override
 	public void scrollToTop(){
+		if (((ScrollableToTop) fragments[pager.getCurrentItem()]).isScrolledToTop()) {
+			int nextPage = (pager.getCurrentItem() + 1) % count;
+			navigateTo(nextPage);
+			return;
+		}
 		((ScrollableToTop) fragments[pager.getCurrentItem()]).scrollToTop();
 	}