Fix d.ts for concat-stream

[Justin Beckwith]

The @types/concat-stream package seems to have problems when using import * as concatStream from 'concat-stream' style imports.

This package needs to be fixed:
https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/concat-stream

The fix likely looks like this:
DefinitelyTyped/DefinitelyTyped#24650

After that's fixed and shipped, we need to update the package and make sure we use import instead of require for the package.

[Justin Beckwith]

Resolved by #94