Remove necessary hashtag, make it optional

[philipbrembeck]

Proposed changes

Get rid of the necessary Hashtag and use endpoint accounts/statuses instead.
The Hashtag could be optionally added in the down_msg or up_msg (proposed in #3 ), but should not be necessary.

Steps

• Find a way to extract a users profile id – without the user having to find it out via the API
  This won't work: https://example.social/api/v1/accounts/@username/statuses
  While this works: https://fosstodon.org/api/v1/accounts/12345678900000000/statuses
• Change the search for hashtag to a profile search (only the last 1-2 posts)