Merge pull request #2658 from kakugiki/master

containerCss backgroundColor: 'transparent'

Author: Uzlopak

src/modules/html.js

@@ -159,7 +159,8 @@
  x: 0,
  y: 0,
  html2canvas: {},
- jsPDF: {}
+ jsPDF: {},
+ backgroundColor: "transparent"
  }
  };
 
@@ -246,7 +247,7 @@
  right: 0,
  top: 0,
  margin: "auto",
- backgroundColor: "white"
+ backgroundColor: this.opt.backgroundColor
  }; // Set the overlay to hidden (could be changed in the future to provide a print preview).
 
  var source = cloneNode(