Tree component in the starter-kit does not behave the same way.

### Issue type

**I'm submitting a ...** (check one with "x")

* [X] bug report

### Issue description

**Current behavior:**
Tree component in the starter-kit does not have arrow pointer and won't expand on mouse click, but expanding the nodes work using keyboard arrow keys.

**Expected behavior:**
Starter-kit tree component to have the same functionality as ngx-admin live demo.

**Steps to reproduce:**
Clone starter-kit
npm install angular-tree-component
Activate starter-kit tree component by adding it to routing and module declarations.

**Related code:**

** pages-routing-module.ts**
```
import { TreeComponent } from './components/tree/tree.component';
...
export const routedComponents = [
TreeComponent,
];
```
** pages-module.ts**
```
import { TreeModule } from 'angular-tree-component';
import { PagesRoutingModule, routedComponents } from './pages-routing.module';
```
The rest of the starter-kit code was not modified.

### Other information:

**npm, node, OS, Browser**
```
Node: v10.5.0
NPM: 6.0.1
OS: Ubuntu 18.04 LTS
Browser: Chrome Version 67.0.3396.87 (Official Build) (64-bit)
```

**Angular, Nebular**
```
"@angular/core": "6.0.0",
"@nebular/auth": "2.0.0-rc.9",
"@nebular/security": "2.0.0-rc.9",
"@nebular/theme": "2.0.0-rc.9",
```