Re-use package.lock.json to point to public sodium-native repository

[MaciejBaj]

Expected behavior

As the package-lock.json was introduced together with the migration to npm v5, we don't have to point to the internal LiskHQ/sodium-native version.

Actual behavior

LiskHQ forked sodium-native repository and froze its dependencies, which doesn't have to happen since package-lock.json is present.

Which version(s) does this affect? (Environment, OS, etc...)

>=1.1.0