[zh_CN] done /zh/models/associations-linking-models-together.rst

I guess all the table alignment issues are actually not issues because the sphinx didn't complain about this in my Vagrant build.  And remember last time you helped fix the table alignment in [/zh/contributing/backwards-compatibility.rst](https://github.com/cakephp/docs/commit/dd6366413e14f38f0b3b71848f5c5c9faad401ca) when I started to contributed to Simplified Chinese translation?  That time the alignment also looks not aligned but it works.  Think it's because the Chinese characters occupy different spaces than western characters.