title: No mixin named nb-install
body: <p>i am using angular5, getting the 'No mixin named nb-install' error when executing npm start or serve</p>
  
  <pre><code>Module build failed:
  undefined
          ^
        No mixin named nb-install
  
  Backtrace:
          stdin:13
        in E:\mrb_bugfixes\bottledepot\src\app\@theme\styles\styles.scss (line 13, column 10)
  </code></pre>
  
  <p>Following is the file named 'styles.scss' i am executing</p>
  
  <pre><code>@import 'themes';
  
  // framework component themes (styles tied to theme variables)
  @import '~@nebular/theme/styles/globals';
  @import '~@nebular/auth/styles/all';
  
  // loading progress bar theme
  @import './pace.theme.scss';
  
  // install the framework and custom global styles
  
  @include nb-install() {
  
  // framework global styles
  @include nb-theme-global();
  @include nb-auth-global();
  
  // loading progress bar
  @include ngx-pace-theme();
  
  .custom-control .custom-control-indicator {
  border-radius: 50%; // TODO: quickfix for 
  https://github.com/akveo/nebular/issues/275
  }
  };
  </code></pre>