Lists of supported URL-s must not have a schema!

"http://" stripped off BMC and Elsevier journal URL lists. README.md
added to openarticlegauge/plugins/resources/ explaining the situation.

BMC tests now pass (broken by previous commit since
openarticlegauge.plugins.bmc.supports_url() would fail because of the
schema specified in the URL-s). Also, www.biomedcentral.com itself was
missing from the URL list, now added.