Disable es3 jshint rule
Disable es3 jshint rule

fixes https://github.com/keystonejs/generator-keystone/issues/123
Out of the box linting fails due to usage of es3 reserved word `import`
by keystone api.

steventux/generator-keystone-content,keystonejs/generator-keystone,keystonejs/generator-keystone,steventux/generator-keystone-content