Textarea: fix clicking on name suggestions

This was broken in c3e9ba6a, which added an onBlur to hide the
suggestions when the textarea loses focus. Unfortunately, this fired
even when the textarea lost focus to its own suggestions box, and that
meant that onSuggestionClick is never called.

Setting a short window in which onSuggestionClick can still happen
before hiding the suggestion area ensures that clicking still works,
while still hiding the suggestions if the user clicks on something else.

Update README.md to match new documentation (missed from previous commit)

Documentation tweaks

used from nginx when Rails fails.

Add a default missing.png header image - fixes #492

Call uniq on the string version of mb_chars tags - fixes #503

Show visibility toggle on videos, show regardless of sensitivity

Also, since the root component connects to the stream that updates home/notification columns,
there is pretty much no case for refreshing those columns beyond initial load. So, move the
loading of those columns into the root component, to prevent unneccessary reloads when switching tabs
on mobile or resizing desktop window between mobile/desktop layouts