Improve OEmbed error handling

[kmcelwee]

• [ ] Create a file reviewed-oembed-errors.txt that lists IDs reviewed in #14.
• [ ] Update collect-twitter-oembeds.py to print out errors that are new.
• [x] Update collect-twitter-oembeds.py to include returned messages with "error" to be included in the "error" field.

[kmcelwee]

"Companies are deleting some tweets" is out of scope. It was convenient to find errors, but this'll get distracting. The last todo was addressed in 027d9d5c74cde3c301087a6173b3d67b503f34c4