title: Viewpageindicator error, TitlePageIndicator is emty
body: <p>Hi im using viewpageindicator and have setup a viewpager and fragments that works like a charm!
  The problem is that I dont seem to get the TitlePageIndicator to work. It is just empty and dosnt show anything.</p>
  
  <pre><code>&lt;android.support.v4.view.ViewPager
          android:id="@+id/pager"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:layout_above="@+id/indicator"
          android:layout_alignParentLeft="true"
          android:layout_below="@+id/textView2" &gt;
  
      &lt;/android.support.v4.view.ViewPager&gt;
  
     &lt;com.viewpagerindicator.TitlePageIndicator
          android:id="@+id/indicator"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:layout_alignParentBottom="true"
          android:layout_alignParentLeft="true"
          android:padding="10dip"
          android:visibility="visible"
          app:linePosition="top" 
          android:theme="@style/CustomUnderlinePageIndicator"/&gt; 
  </code></pre>
  
  <p>suspect that something goes wrong with the styles. i use the style file from the viewpageindicator sample.</p>
  
  <p>When i exicute this code I get following logcat error :</p>
  
  <pre><code>mPager = (ViewPager)findViewById(R.id.pager);
  
      mPager.setAdapter(mAdapter);
  
      mIndicator = (TabPageIndicator)findViewById(R.id.indicator);
      mIndicator.setViewPager(mPager);
  </code></pre>
  
  <p>error: java.lang.ClassCastException: com.viewpagerindicator.TitlePageIndicator cannot be cast to com.viewpagerindicator.TabPageIndicator</p>