Betula v0.5.0

This tag is the first pre-release of Betula. It marks the
end of the Alpha era, and the beginning of the Beta era.

Release notes:

=> https://betula.mycorrhiza.wiki/v0.5.0.html

Timur Ismagilov (77):
      Write README.md
      Fix Markdown
      Implement saving and listing the links
      Choose LICENSE
      Add globes and timestamps, style a bit
      Move the Add Link form on a separate page
      Fit layout for smaller screens
      Implement Go-links
      Update README.md
      Implement post views
      Do some visual design, adapt for mobile
      Validate added URL
      Write template utilities
      Implement /about
      Change naming in the DB to PascalCase
      Show Add link in <main>, when no links saved
      Implement categories display
      Name categories categories properly
      Draw categories of the post in cute little gray pills
      Work on visuals
      Implement category views
      Reduce boilerplate
      List categories on /cat/
      Rename Add link to Save link
      Implement the auth package
      Implement the register form
      Implement the authentication backend
      Implement the authentication views, but broken
      Fix auth
      Get rid of unneeded variables in package auth
      Show private posts to the authorized only
      Implement the 404 page
      Save description of links
      Edit links
      Save link: Refactor and redesign
      Save link: Redesign
      Redesign the way posts look
      Reverse the order of posts in feeds
      Hide protocols for links
      Center main, use less white background
      Add Betula title to <nav>
      Make further design updates
      Add accessible description for the globi and locks
      Render Mycomarkup in descriptions
      Fix at least three bugs
      Make the category input
      Store categories without ids
      Implement category editing
      Fix empty category being allowed
      Make forms look a little more consistent
      Save links public by default
      Fix categories not being saved for new posts
      Change textarea's font to sans-serif
      Limit the number of concurrent writes
      Revert "Limit the number of concurrent writes"
      Do not use channels anymore
      Limit the number of concurrent writes
      Draft the deletion form
      Implement migration 0 -> 1
      Fix queries to they consider deleted posts
      Implement deletion
      Hide private categories for the unauthorized
      Fix extra long things breaking layout
      Implement Post.FixMeUp
      Update Mycomarkup to v5.4.0
      Make the heading bigger on standalone post pages
      Add basic microformats2 classes
      Show post count on /cat/
      Turn off auto complete for the link form
      Ignore all .betula files in .gitignore
      Embrace border-box
      Change microformats
      Deprecate .src-url class
      Refactor /cat/
      Update README.md
      Show 404 for non-numeric /post/...
      Go from alpha to beta