Adding --updatefeed [author name]

[stevenleeg]

Here's my go at adding the ability to refresh a given feed. I'm not exactly sure how useful this could be, given that the server doubles as an HTTP server and feed manager (maybe this is something that should be in a separate exec file?).

It's pretty straightforward though. It removes all posts by a given author's name and then programmatically sets the --updateposts flag to true. I wasn't sure how else to identify feeds, as source field was always null for items in blogpost in my local db.

Anyways, feel free to merge if you think it may be useful!

Edit: Github sent this before I finished writing this :-1:, so ignore whatever email you got for it.