sets needed position: relative to fixes #2007

__tests__/integration/mirador/embedding.html

@@ -12,11 +12,13 @@
      #instanceOne {
        width: 100%;
        height: 50%;
+       position: relative;
      }
      #instanceTwo {
        margin: 0 auto;
        width: 800px;
        height: 600px;
+       position: relative;
      }
      .mirador-app {
        border: 2px solid black;