Add link to admin, and add PostViewAdmin and ImageAdmin
Documentation
Fix bug of case of zero posts showing all tags
Add max image width to posts
Remove admin for UploadedImage and PostView.

These are low-level enough that they should seldom be touched, and if so,
should be done manually through the MySQL database (e.g. since to delete or
change uploaded images, they must also be changed through AWS S3)
Update README
Update README
Merge branch 'master' into experiment