Travis CI failing on PRs due to confidential env variables not being shared outside repo

[sandervanhooft]

Cashier Mollie tests run against Mollie's API.

The credentials for this are stored confidentially in Travis, as to not overload the test account.

The downside of this is that PRs (hosted at the contributor's repo) do not have access to these credentials, and these tests always fail. (See #33 for example).

[sandervanhooft]

FYI @vblinden.

[sandervanhooft]

@willemstuursma do you have a suggestion here? Just open up the credentials?

[willemstuursma]

Skip the tests if in a PR.

[sandervanhooft]

👍 Good one. Will set up a dev branch as the default.