add spec
add spec

@KitaitiMakoto

I add 1 pending test, i can not work with...
Do you guess where i am wrong... :S
extract as method render_not_found
fix test as not existed snippedt

refs: https://travis-ci.org/iiirc/iiirc/jobs/7261642
Use render_views for API specs
move content-type test and add render_template
Merge branch 'improvement-the-coverage-rate-for-api-snippet'

* improvement-the-coverage-rate-for-api-snippet:
  move content-type test and add render_template
  Use render_views for API specs
  fix test as not existed snippedt
  extract as method render_not_found
  add spec
  add spec

Conflicts:
	spec/controllers/api/snippets_controller_spec.rb