added new style PEG video

Author: simongravelle

docs/avatars/level2/stretching-a-polymer/stretching-polymer-gromacs.png

@@ -55,12 +55,12 @@ <h2>
                         </article>
                         <article class="style1">
                             <span class="image">
-                                <img src="sphinx/source/tutorials/figures/level3/solvation-energy/no-field-dark.png" alt="gromacs tutorial logo" />
+                                <img src="avatars/level2/stretching-a-polymer/stretching-polymer-gromacs.png" alt="gromacs tutorial logo" />
                             </span>
-                            <a href="sphinx/build/html/tutorials/level3/solvation-energy.html">
+                            <a href="sphinx/build/html/tutorials/level2/stretching-a-polymer.html">
                                 <div class="content">
                                     <p align="left">
-                                        Calculating the <b>solvation free energy</b> of a graphene-like molecule
+                                        Stretching a <b>polymer</b> in water
                                     </p>
                                 </div>
                             </a>