Bump ms version to add support for negative numbers

[MitMaro]

What

zeit/[email protected] added full support for negative numbers, but the package is set to zeit/[email protected]. This can be useful when defining a nbf value with zeit/ms, ie. nbf = '-30m'.

Due to npm's dependency de-duping this can sometimes result in this library using version zeit/[email protected] instead of zeit/[email protected] resulting in invalid results. In my case visionmedia/debug had their version on zeit/ms pinned to 2.0.0.

This PR bumps the version to zeit/[email protected] to ensure that negative numbers in zeit/ms format work as expected.

Dedupe Example

$ npm show ms version
2.1.1

$ npm list ms
@org/[email protected] /Users/mitmaro/code/org/auth-lib
├─┬ [email protected]
│ └── [email protected]
└─┬ [email protected]
  └── [email protected]  deduped

[ziluvatar]

Thanks @MitMaro