Make things line up on the usage page

The mixture of three column/two column layouts on this page has always
looked a bit disjointed. And since the left column will only even
contain the names of months, which are short, it doesn’t need a full
half of the page width.

app/assets/stylesheets/components/table.scss

@@ -98,6 +98,20 @@
 
 }
 
+.usage-table {
+
+  .table-field-heading-first {
+    width: 35%;  // 33.33% + fudge
+  }
+
+  .table-row {
+    th {
+      width: 17.5%  // 16.67% + fudge
+    }
+  }
+
+}
+
 %table-field,
 .table-field {