License/redistributability of data in test/files #158

Hi, there are several files in test/files, such as test/files/cdec/historical/sensors.htm, which comes from upstream sources and needs documentation on its license/redistributability. I'm assuming a lot of it is going to be some sort of public domain, but right now it's undocumented.

I'm packaging ulmo for Debian (so it'll likely be in Ubuntu 18.10 and onwards), and because of this, I'm going to have to exclude test/files, but I'd like to include it if possible in the future once the provenance of the data and associated files is cleared up.