Use {} instead of void for component state to avoid build errors.

[rozzzly]

Updates to TypeScript/the React type definitions have caused issues for me when a component uses void instead of {} to indicate that a component doesn't make use of state. With default generics in typescript@2.3 and the subsequent update over at DefinitelyTyped you can just omit the void so your class declaration looks like:

class MyComponent extends React<MyComponentProps> {
}

And things will work just fine. However so the type definitions in this repo are more backwards compatible I opte to substitute {} in for void so pre 2.3 consumers don't have any issues.

Here's the build error I get when a component uses void:

[at-loader] Checking finished with 2 errors
[at-loader] ./src/common/components/Modal/index.tsx:107:13
    TS2605: JSX element type 'Fill' is not a constructor function for JSX elements.
  Types of property 'setState' are incompatible.
    Type '{ <K extends never>(f: (prevState: void, props: Props) => Pick<void, K>, callback?: () => any): v...' is not assignable to type '{ <K extends never>(f: (prevState: {}, props: any) => Pic
k<{}, K>, callback?: () => any): void; <...'.
      Types of parameters 'f' and 'f' are incompatible.
        Types of parameters 'prevState' and 'prevState' are incompatible.
          Type 'void' is not assignable to type '{}'.

[at-loader] ./src/common/components/Modal/index.tsx:139:13
    TS2605: JSX element type 'Fill' is not a constructor function for JSX elements.

[rozzzly]

If someone wanted to take a look at the failing tests, I'd appreciate it. It looks like they're related to the type definitions for the project's dependencies and not due to the change I made.

[camwest]

@rozzzly can you try again with the latest master?

[rozzzly]

@camwest looks like everything is good to go

[rozzzly]

@camwest could you publish a new version to NPM? thanks