title: The banner not showing with my id from adMob Ionic 3
body: <p>when i'll try run my application in my device with this code:</p>
  
  <p><code>ionic cordova build android</code></p>
  
  <p>It is generated an APK and I installed in my device. When i build with this code, the Ads works:</p>
  
  <p><code>
    showAd() {
      const bannerConfig: AdMobFreeBannerConfig = {
        isTesting: true,
        autoShow: true
       };
       this.admobFree.banner.config(bannerConfig);
       this.admobFree.banner.prepare()
         .then(() =&gt; {
           // banner Ad is ready
           // if we set autoShow to false, then we will need to call the show method here
         })
         .catch(e =&gt; console.log(e));
    }
  </code></p>
  
  <p>When I build with this other code, the Ads not show:</p>
  
  <p><code>
    showAd() {
      const bannerConfig: AdMobFreeBannerConfig = {
        id: 'MY-ID-FROM-ADMOB',
        isTesting: false,
        autoShow: true
       };
       this.admobFree.banner.config(bannerConfig);
       this.admobFree.banner.prepare()
         .then(() =&gt; {
           // banner Ad is ready
           // if we set autoShow to false, then we will need to call the show method here
         })
         .catch(e =&gt; console.log(e));
    }
  </code></p>
  
  <p>Someone help me, please...</p>
  
  <p>Sorry if I wrote wrong something, my english is not very well...</p>