Use https API URL to allow use of non-creator user keys

This works with existing keys AND allows non-creator keys to have messages
published.

i.e. it resolves this error message
    {
        errors    [
            [0] "messages to users other than the creator of this application (E2P) must be sent over SSL to https://api.pushover.net/"
        ],
        request   "e0995xxxxxxxxxxxxxxxxxxxxxxxxxxx",
        status    0
    }