chore(deps): update dependency @types/koa-bodyparser to a valid 4.2.1… (#2217)
chore(deps): update dependency @types/koa-bodyparser to a valid 4.2.1… (#2217)

… version

This PR should hopefully correct some typing issues we are currently facing.

The problem:
- this package references v5.0.1 for @types/koa-bodyparser
- when we start our server that also uses koa-bodyparser for non-graphql routes, the type for koa.Request sets the "body" field to:

```
declare module "koa" {
    interface Request {
        body: {} | null | undefined;
        rawBody: {} | null | undefined;
    }
}
```

Which breaks our type defs for koa-bodyparser as we actually want "body" to be set to "any."

The v5.0.1 that was originally placed here is no longer "latest" and they have published a new v4 version that has the correct typing for koa-bodyparser (setting body to any). - https://www.npmjs.com/package/@types/koa-bodyparser

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TODO:

* [ ] Update CHANGELOG.md with your change (include reference to issue & this PR)
* [x] Make sure all of the significant new logic is covered by tests
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apollostack/apollo-server