title: ngx-bootstrap tooltip not showing up in angular2
body: <p>I have an angular-cli application and need to include tooltip for a button
  here is my app.module.ts</p>
  
  <pre><code>import { BrowserModule } from '@angular/platform-browser';
  import { NgModule } from '@angular/core';
  import { FormsModule } from '@angular/forms';
  import { HttpModule } from '@angular/http';
  import {BenefitsManagementModule} from './benefits-management/benefits-management.module';
  import { AppComponent } from './app.component';
  import { LoginComponent } from './login/login.component';
  import { AuthService } from './auth/auth.service';
  import {AppRoutingModule} from './app-routing.module';
  import { TooltipModule } from 'ngx-bootstrap';
  
  @NgModule({
    declarations: [
      AppComponent,
      LoginComponent
    ],
    imports: [
      BrowserModule,
      FormsModule,
      HttpModule,
      BenefitsManagementModule,
      AppRoutingModule,
       TooltipModule.forRoot()
    ],
    providers: [
      AuthService
    ],
    bootstrap: [AppComponent]
  })
  export class AppModule { };
  </code></pre>
  
  <p>here is my html for button</p>
  
  <p></p>
  
  <p><code>&lt;button type="submit"  [disabled]="!benefitScheduleForm.valid" class="btn btn-md btn-primary" style="float:left;"&gt;Add&lt;/button&gt;
    &lt;button type="button" tooltip="mytooltip"  class="btn btn-md btn-primary" style="float:right;" (click)="cancel()"&gt;Cancel&lt;/button&gt;
  &lt;/div&gt;</code></p>
  
  <p>Can anybody help me out?</p>