Import specifically `createHash`, rather than `* as crypto` from `crypto`.
Import specifically `createHash`, rather than `* as crypto` from `crypto`.

This silences the deprecation messages which have been showing up in recent
local development on the new request pipeline work.  e.g.:

> ```
> [DEP0010] DeprecationWarning: crypto.createCredentials is deprecated.
>   Use tls.createSecureContext instead.
> [DEP0011] DeprecationWarning:
>   crypto.Credentials is deprecated. Use tls.SecureContext instead.
> ```

apollostack/apollo-server