Revert "never overwrite"

This reverts commit 6b67321bf566aa03611e8476f7ca3e9920b6b64c.
fix minor bugs
play URL bug
update README, toolchain
fix minor bugs
fix MIME types
fix minor bugs, add opus warn
remove webp, scale options
add favicon.ico generation, meta description
fix html to validate
nginx.sh: remove extraneous whitespace
warn-container -> interstitial, misc css fixes
misc js bugs
prep spinner
fix minor bug, add robots.txt
Stuff.
Stuff.
Build stuff.
Update README
Minor refactoring.