Added links to codepen, updated readme.md, added links to additional demos

Author: AndreyChayko

README.md

@@ -15,7 +15,8 @@ Demo Angular UI Router: http://angular-data-grid.github.io/demo/bootstrap/ui-rou
  - Does not have any hard-coded template so you can choose any mark-up you need, from basic `<table>` layout to any `<div>` structure.
  - Easily switch between the most popular Bootstrap and Google Material theming, or apply your own CSS theme just by changing several CSS classes.
  - Built-in sync with browser address bar (URL), so you can copy-n-paste sorting/filtering/pagination results URL and open it in other browser / send to anyone - even if pagination / filtering are done on a client-side. [See details](#url-synchronization)
- - Support of [Angular UI Router](https://github.com/angular-ui/ui-router) navigation. 
+ - Support of [Angular UI Router](https://github.com/angular-ui/ui-router) navigation.
+ - Optional support of fixed header table: [bootstrap Demo](https://github.com/angular-data-grid/demo/fixed-header/bootstrap-grid.html) [Material Design Demo](https://github.com/angular-data-grid/demo/fixed-header/angular-md-grid.html)
  - Unlike most part of other Angular DataGrids, we intentionally use non-isolated scope of the directive to maximize flexibility, so it can be easily synchronized with any data changes inside your controller. 
  NOTE! With great power comes great responsibility, so use non-isolated API wisely.
 

demo/bootstrap/index.html

@@ -48,6 +48,9 @@ <h4>Additional Demos</h4>
         <li>
             <a href="ui-router.html" target="_blank">UI Router plus server pagination</a>
         </li>
+        <li>
+            <a href="../fixed-header/bootstrap-grid.html">Fixed header table</a>
+        </li>
     </ul>
     <hr>
     <div class="row">

demo/fixed-header/angular-md-grid.html

@@ -245,9 +245,9 @@ <h4>Using Stand-alone Directive</h4>
         <hr>
         <md-button class="md-raised md-primary" ng-click="showCode = !showCode">CodePen</md-button>
         <div ng-show="showCode" class="codepen-wrap">
-            <p data-height="768" data-theme-id="21603" data-slug-hash="eJWWpM" data-default-tab="html"
+            <p data-height="768" data-theme-id="21603" data-slug-hash="bqXarG" data-default-tab="html"
                data-user="AngularDataGrid" class='codepen'>See the Pen <a
-                    href='http://codepen.io/AngularDataGrid/pen/eJWWpM'>eJWWpM</a> by AngularDataGrid (<a
+                    href='http://codepen.io/AngularDataGrid/pen/bqXarG'>eJWWpM</a> by AngularDataGrid (<a
                     href='http://codepen.io/AngularDataGrid'>@AngularDataGrid</a>) on <a href='http://codepen.io'>CodePen</a>.
             </p>
             <script async src="//assets.codepen.io/assets/embed/ei.js"></script>

demo/fixed-header/bootstrap-grid.html

@@ -285,8 +285,8 @@ <h4>Additional Demos</h4>
     <div>
         <button class="btn btn-info margin-bottom-basic" ng-click="showCode = !showCode">CodePen</button>
         <div ng-show="showCode">
-            <p data-height="768" data-theme-id="21603" data-slug-hash="xZddZm" data-default-tab="html" data-user="AngularDataGrid" class='codepen'>See the Pen <a
-                    href='http://codepen.io/AngularDataGrid/pen/xZddZm/'>xZddZm</a> by AngularDataGrid (<a href='http://codepen.io/AngularDataGrid'>@AngularDataGrid</a>) on <a href='http://codepen.io'>CodePen</a>.</p>
+            <p data-height="768" data-theme-id="21603" data-slug-hash="qrGXRL" data-default-tab="html" data-user="AngularDataGrid" class='codepen'>See the Pen <a
+                    href='http://codepen.io/AngularDataGrid/pen/qrGXRL/'>xZddZm</a> by AngularDataGrid (<a href='http://codepen.io/AngularDataGrid'>@AngularDataGrid</a>) on <a href='http://codepen.io'>CodePen</a>.</p>
             <script async src="//assets.codepen.io/assets/embed/ei.js"></script>
         </div>
     </div>

demo/material/index.html

@@ -44,6 +44,12 @@ <h4>Angular Data Grid sample using Material Design styling</h4>
                     <a href="https://github.com/angular-data-grid/angular-data-grid.github.io"
                        target="_blank">Project GitHub</a></p>
             </div>
+            <h4>Additional Demos</h4>
+            <ul>
+                <li>
+                    <a href="../fixed-header/angular-md-grid.html">Fixed header table</a>
+                </li>
+            </ul>
             <hr>
             <div layout-gt-xs="row" layout-xs="column" layout-align="stretch center">
                 <div  layout="row" layout-align="center start">