Change task-list adding dialog style.

src/app/task-lists/add-task-list/add-task-list.component.html

@@ -1,3 +1,4 @@
+<h2>Création d'une task-list</h2>
 <form [formGroup]="addTaskListFormGroup" (submit)="onSubmit()" ngNativeValidate>
   <p>
     <mat-form-field>
@@ -8,8 +9,8 @@
       </mat-error>
     </mat-form-field>
   </p>
-  <div>
-    <button mat-raised-button type="button" (click)="close()">Annuler</button>
-    <button mat-raised-button type="submit">Créer une liste</button>
+  <div class="actions">
+    <button class="raised" type="button" (click)="close()">Annuler</button>
+    <button class="raised"  type="submit">Créer une liste</button>
   </div>
 </form>