Fix XHR failure for file: protocol.
Add Duan Yao to AUTHORS
Add svg-nodes-limit option to avoid overly complicated svg background.
fix travis build
Move BackgroundRenderer fallback logic to HTMLRenderer.
Implement --svg-embed-bitmap: saving bitmaps in svg as external files.
Some coding style improvements
Fix bad usage of html_renderer->str_fmt() in get_bitmap_path(); add prefix to bitmap file name.
Improve help texts for --svg-node-count-limit and --svg-embed-bitmap; rename --svg-nodes-limit to --svg-node-count-limit.
Code cleaning.
Merge pull request #364 from duanyao/svg_extern_bitmap

Svg extern bitmap & svg node count limit