Breaking changes

• c83140f dropped the support of Node.js 4.x.
• 4e2cd77 dropped the support of ESLint 3.x and 4.x. And it upgraded espree and eslint-scope packages, vue-eslint-parser is using internally, to 4.0.0. This means it dropped the support of parserOptions.ecmaFeatures.experimentalObjectRestSpread option. Use ecmaVersion option instead.
• 87efc6d added the support of slot-scope attribute to define variables which are available on inside of the element. The slot-scope attribute is expressed as new VSlotScopeExpression node. And it changed the AST of <template scope> attribute to the VSlotScopeExpression node.