title: Format lowercased string to capitalize the begining of each sentence
body: <p>I have a string like </p>
  
  <p><code>FIRST SENTENCE. SECOND SENTENCE.</code></p>
  
  <p>I want to <em>lowercase</em> the string in that way to capitalize the first letter of each sentence.</p>
  
  <p>For example:</p>
  
  <pre><code>string = string.toLowerCase().capitalize();
  </code></pre>
  
  <p>only the first sentence is capitalized.</p>
  
  <p>I have the </p>
  
  <p>String.prototype.capitalize = function() {
          return this.charAt(0).toUpperCase() + this.slice(1);
      }</p>
  
  <p>function</p>
  
  <p>Does anyone know how to solve?</p>