Flow props are now a generic type

[iainbeeston]

In the latest versions of flow, proptypes are no longer a class property when using es6 classes, eg.

export type Props = {
  foo: number
}

class MyComponent extends React.Component {
  props: Props
}

Instead React.Component is a generic type, and it expects the props to be passed into that instead:

export type Props = {
  foo: number
}

class MyComponent extends React.Component<Props> {
}

The codemod is currently doing the former, but I suspect it should be either updated to do the latter, or have a flag that lets it do either depending on the flow version(?).

[kangax]

Added #23 that fixes it