title: has no exported member 'ComponentsHelper
body: <p>I got an error when I run 'npm start':</p>
  
  <blockquote>
    <p>ERROR in [at-loader] src/app/app.component.ts:7:10 
        Module '"/Users/xx/Documents/sourcecode/xx/xx/xx/node_modules/ng2-bootstrap/index"' has no exported member 'ComponentsHelper'.</p>
    
    <p>line 7 in app.component.ts is 
    import { ComponentsHelper } from 'ng2-bootstrap';</p>
  </blockquote>
  
  <p>In my package.json, my version is  "ng2-bootstrap": "^1.2.4".</p>
  
  <p>Any help? thanks in advance.</p>