CJK support using the xeCJK package.

Getting xeCJK to play nicely with polyglossia is somewhat fraught. See:
http://tex.stackexchange.com/questions/45331/combining-chinese-japanese-and-korean-text-with-xecjk
http://tex.stackexchange.com/questions/36878/xecjk-messes-with-punctuation

Updated gammalatex so that we can set the TEXINPUTS path.  See:
https://github.com/gammasoft/latex/pull/3

Added some CJK fonts to the README and travis config.

Note that Parsoid doesn't support LanguageConverter yet, so we can't
properly handle Simplified -vs- Traditional Chinese.  We'll revisit
that once the Parsoid support is in place
(https://bugzilla.wikimedia.org/show_bug.cgi?id=41716).

Change-Id: Icd770deae3a8307721c1417754285754e498a2c2