Merge branch 'dev'

* dev: (56 commits)
  add snippets path to readme as sample
  add sinppets to docs
  fix tests
  remove chinese documentation links
  typos
  update docs
  remove zh docs!
  update english version documents, and I SHOULD GOTO lunch!
  remove multiple spaces for generated sql
  update the simple samples
  update tables.sql
  upgrade to v0.5.0 - Beta
  update messageboard examples
  fix typos
  update changes: v0.5.0
  the tests are basic ok
  tests for functions and runtime
  fix field set instance attrs
  having method missing
  add sql literal object
  ...
fix tests 91.1 https://travis-ci.org/hit9/CURD.py/jobs/23593290
update building status image to master branch
why #92.2 is broking?
fix #https://travis-ci.org/hit9/CURD.py/builds/23595182
update readme for beta version