fix(sortable): Changed reference to BrowserModule to CommonModule instead (#1503)

* Library Modules should not import BrowserModule anywhere

Caused error: 
`BrowserModule has already been loaded. If you need access to common directives such as NgIf and NgFor from a lazy loaded module, import CommonModule instead.`

After trying on lazy loaded app, that had `Ng2BootstrapModule.forRoot()` imported in root App Module.

* changed code styling to be consistent with the rest

Hopefully it will pass CI tests now!

Author: somombo

src/sortable/sortable.module.ts

@@ -1,12 +1,12 @@
 import { NgModule, ModuleWithProviders } from '@angular/core';
-import { BrowserModule } from '@angular/platform-browser';
+import { CommonModule } from '@angular/common';
 
 import { SortableComponent } from './sortable.component';
 import { DraggableItemService } from './draggable-item.service';
 
 @NgModule({
     declarations: [SortableComponent],
-    imports: [BrowserModule],
+    imports: [CommonModule],
     exports: [SortableComponent]
 })
 export class SortableModule {