corrected error in the chart path in the charts pages (#1581)

pages/charts/chartjs.html

@@ -704,7 +704,7 @@
 <!-- Bootstrap 3.3.7 -->
 <script src="../../bower_components/bootstrap/dist/js/bootstrap.min.js"></script>
 <!-- ChartJS -->
-<script src="../../bower_components/Chart.js/Chart.js"></script>
+<script src="../../bower_components/chart.js/Chart.js"></script>
 <!-- FastClick -->
 <script src="../../bower_components/fastclick/lib/fastclick.js"></script>
 <!-- AdminLTE App -->