It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
* Chinese segmenetation will continue to rely on cppjieba
* Japanese segmentation will use our port of TinySegmenter
* Korean currently does not rely on segmentation which was dropped in c677877e4f
* SiteSetting.search_tokenize_chinese_japanese_korean has been split
into SiteSetting.search_tokenize_chinese and
SiteSetting.search_tokenize_japanese respectively