title: Count letters in a word
body: <p>I want to count the small letter alphabets present in a string. Say I have:</p>
  
  <pre><code>a = "SaMarMiShrA"
  </code></pre>
  
  <p>I know that a.count("a-z") will give the answer. But how to do without using this without inbuilt methods.</p>
  
  <p>Then,</p>
  
  <pre><code>def count_small_letters
    #code
  end
  a.count_small_letters
  </code></pre>
  
  <p>should return <code>6</code> since in <code>"SaMarMiShrA"</code>, the number of small letter alphabets is 6. Please suggest a solution for this.</p>