v1.5.0 Not perfectly compatible with older versions

[renshaomeng]

When I update （ from1.4.1 to 1.5.0）, I encounter this problem => ‘.VueAuthenticate is not a constructor’

1.4.1=>1.5.0 Remove 'export {VueAuthenticate}', need modify the import code when updating the version.

https://docs.npmjs.com/about-semantic-versioning