title: angular translate instant method does not work
body: <p>We have a website with angular translate. It works perfectly. We have a variable that we want to fixate with a certain language key. Let's say the site's language has 'en' and 'zh' as options, I want a certain translation to return with 'zh' no matter the language choice. </p>
  
  <p>By browsing the <a href="http://angular-translate.github.io/docs/#/api/pascalprecht.translate.%24translate" rel="nofollow">API reference</a>, I found a method called Instant to do just that. However, it doesn't work when we try to call</p>
  
  <pre><code>$translate.instant('zh', 'TRANSLATION_ID')
  </code></pre>
  
  <p>It returns an error of </p>
  
  <pre><code>TypeError: Object function (a,b,e){var f=d?n[d]:n,i=e?w[e]:u;if(f&amp;&amp;f.hasOwnProperty(a))return i.interpolate(f[a],b);if(h&amp;&amp;!v&amp;&amp;g.get(h)(a,d),d&amp;&amp;c&amp;&amp;d!==c){var j=n[c][a];if(j){var k;return i.setLocale(c),k=i.interpolate(j,b),i.setLocale(d),k}}return l&amp;&amp;(a=[l,a...&lt;omitted&gt;...a} has no method 'instant'
  </code></pre>
  
  <p>I wonder how to use the isntant method correctly.</p>