Update Readme

No code changes. Just wanted to publish a new version to npm that updated the readme to reflect benchmark numbers found running against v2.0.0.

Standardize Value Return and Metadata

New Feature
When calling value, the value will always be null, eliminating the need to worry about undefined vs null. If that information is required, you can call rawValue in order to get it.

Metadata
Updated keywords, added benchmark numbers, and explicitly added the MIT license.

Added Immediate Resolve

This release updates:

1. The readme to have clearer examples.
2. Adds feature to immediately resolve paths to reduce the memory footprint if the path is known ahead of time.