BUG: JSX allow tag use `class` property

[soulteary]

Node ver: 5.0.0

Babel Deps:

• "babel-cli": "^6.4.0",
  

• "babel-core": "^6.3.26",
  

• "babel-eslint": "^5.0.0-beta6",
  

• "babel-loader": "^6.2.0",
  

• "babel-plugin-add-module-exports": "^0.1.2",
  

• "babel-polyfill": "^6.3.14",
  

• "babel-preset-es2015": "^6.3.13",
  

• "babel-preset-react": "^6.3.13",
  

• "babel-preset-react-hmre": "^1.0.1",
  

• "babel-preset-stage-0": "^6.3.13"
  

It seems cause by custom html tag.

[jimfb]

Not a bug, duplicate of #4933

[soulteary]

@jimfb thx