fix[okta-react-native]: Lock to 0.55.4, add package-lock (#239)

Tests have started failing (see [Build #699](https://travis-ci.org/okta/okta-oidc-js/builds/401943311)).

I tried upgrading the jest and/or the babel plugins, per these threads:

facebook/react-native#19859
jestjs/jest#6505

But I didn't have any luck.  Locking to the 0.55 series of react-native does seem to fix this problem

Author: robertjd