Display latest version in docs

@harvesthq/chosen-developers This fixes #1541.

The version number gets update via [grunt task](https://github.com/harvesthq/chosen/compare/display_latest_version_in_docs?expand=1#L0R82). This will run within the [`prep_release`](https://github.com/harvesthq/chosen/compare/display_latest_version_in_docs?expand=1#L0R109) task.