Fixed endless scroll loading next page too eagerly
Removed tag input focusing in post upload

This caused multiple problems with too eager scrolling:
- adding a new post to upload queue scrolled the site to the tag input
- problems on android, where keyboard can change viewport size on focus
Changed post upload stop button to act immediately
Made post upload stop button abort current AJAX
Added 404 page
Fixed cursor for disabled prev/next post links
Fixed unbinding keyboard shortcuts
Added autocomplete to tag relations
Fixed tags being able to relate to themselves
Changed tag presenter to show meaningful errors
Improved message when renaming tag to existing one
Fixed autocomplete resetting if list didn't change
Changed post upload to select first, not last row
Fixed post upload keeping tag suggestions
Updated mousetrap to newest version

This removes need for my fix in keyboard.js: ccampbell/mousetrap#53
Improved keyboard shortcuts in post upload
Fixed images used fadein even if loaded from cache
Added README
Improved gruntfile
Added logo to README