title: ngbTypeahead not working with Angular 6 and ng-bootstrap
body: <p>I am trying to use <code>ngbTypeahead</code> on a basic Angular 6 application.  There aren't a whole lot of other dependencies in the application.  I keep getting the following method signature not found error...</p>
  
  <pre><code>ERROR TypeError: Object(...)(...) is not a function
  at Observable.push../node_modules/rxjs/_esm5/internal/Observable.js.Observable.pipe (Observable.js:91)
  </code></pre>
  
  <p>If I follow this line it ends up at this code which is the method it is looking for.</p>
  
  <pre><code>return pipeFromArray(operations)(this);
  </code></pre>
  
  <p>Here are the imports</p>
  
  <pre><code>import { Component, OnInit } from '@angular/core';
  import {Observable} from 'rxjs';
  import {debounceTime, map} from 'rxjs/operators';
  </code></pre>
  
  <p>Here is my package.json</p>
  
  <pre><code>{
    "name": "myapp",
    "version": "1.0.0",
    "scripts": {
      "ng": "ng",
      "start": "ng serve --proxy-config proxy.conf.json",
      "build": "ng build",
      "test": "ng test",
      "lint": "ng lint",
      "e2e": "ng e2e"
    },
    "private": true,
    "dependencies": {
      "@angular/animations": "^6.1.0",
      "@angular/common": "^6.1.0",
      "@angular/compiler": "^6.1.0",
      "@angular/core": "^6.1.0",
      "@angular/forms": "^6.1.0",
      "@angular/http": "^6.1.0",
      "@angular/platform-browser": "^6.1.0",
      "@angular/platform-browser-dynamic": "^6.1.0",
      "@angular/router": "^6.1.0",
      "@ng-bootstrap/ng-bootstrap": "^3.0",
      "core-js": "^2.5.4",
      "rxjs": "^6.1.0",
      "rxjs-compat": "^6.1.0",
      "zone.js": "~0.8.26"
    },
    "devDependencies": {
      "@angular-devkit/build-angular": "~0.7.0",
      "@angular/cli": "~6.1.2",
      "@angular/compiler-cli": "^6.1.0",
      "@angular/language-service": "^6.1.0",
      "@types/jasmine": "~2.8.6",
      "@types/jasminewd2": "~2.0.3",
      "@types/node": "~8.9.4",
      "codelyzer": "~4.2.1",
      "jasmine-core": "~2.99.1",
      "jasmine-spec-reporter": "~4.2.1",
      "karma": "~1.7.1",
      "karma-chrome-launcher": "~2.2.0",
      "karma-coverage-istanbul-reporter": "~2.0.0",
      "karma-jasmine": "~1.1.1",
      "karma-jasmine-html-reporter": "^0.2.2",
      "protractor": "~5.3.0",
      "ts-node": "~5.0.1",
      "tslint": "~5.9.1",
      "typescript": "~2.7.2"
    }
  }
  </code></pre>