Store a copy of Powerhouse Museum TSV in assets

[wcaleb]

The phm-collection.tsv dataset used in the Open Refine lesson appears to be missing. We have been saying that we have a copy available on our site, but we don't. So we need to download the collection or check to see if the one mentioned by @acrymble in #390 is the one we need (renamed from txt to tsv perhaps?).

[wcaleb]

@acrymble I'm noticing now that an earlier paragraph in the lesson directs users to find the file here at a FreeYourMetadata link. It looks like the file in question is 56 MB---pretty large for us to store in our repo, but not impossible, I think. So should we just put a copy of the TSV file available on that page in our assets folder? Or are we reasonably confident that it will be reliably available from the FreeYourMetadata site?

[fredgibbs]

since this is a live issue, i would say that we should get in the habit of storing all dependent resources locally. ideally, we could use a portion of the this tsv file--easy to do if we're hosting it ourselves and can edit it--probably all 56 MB isn't necessary and could actually be slightly problematic for people with older machines.

[mdlincoln]

I agree that it's a good policy to try and host copies of lesson data here. The powerhouse data is on the large side of things, and it's a good idea in the future to tailor lesson data to be just the amount needed to be effective. But it's no issue to put a copy here (and that freeyourmetadata site has very slow download speeds, so I'd feel much more comfortable having a copy here anyway)