采用 xeCJK，以便更灵活地分别设置中英文字体

Use xeCJK to define Chinese and English fonts independently.

Also, further revise font setup in template as a proof of concept.

我只是在试验使用 EBGaramond、Cantarell 和中文字体的搭配效果，作为参考。
欢迎随意选择其他字体。

- As a proof-of-concept, use EBGaramond as main font
  and Canterell as bold font for non-CJK text.

- Also, try "AR PL KaitiM GB" for CJK "italic" font

- Use XeTeXinterchartokens mechanism to display
  Miscellaneous Symbols and Dingbats like ⚠ ☢ ☠ ✔
  correctly.  "DejaVu Sans" contains these glyphs
  and is chosen as an example; feel free to choose
  another font.
  See [Font substitution with XeLaTeX](http://tex.stackexchange.com/questions/23049/font-substitution-with-xelatex)
    
- Add a note about jjgod's patches to xdvipdfmx in XeTeX
  as a possible solution to using Source Sans Han S
  in the near future.