Merge pull request #1059 from edx/mjevtic/receipt-page-css-fix

Fix the receipt page style when the footer is displayed

ecommerce/static/sass/partials/views/_receipt.scss

 .receipt {
+    margin-bottom: 20px;
+
     background-color: #ffffff;
     font-family: $font-family-sans-serif;
     line-height: 1em;