Show block type on tooltip for copy/remove.
Move copy button to more discoverable position.
On hovering over copy, preview what will be copied
Use proper api to enable paste button
Disable the copy button once text has been copied.
Add "flash" feature to toolbar.

This allows a plugin to alert the user by flashing a button. What it really
does is intermittently apply a class to the button, which you can then
style as you prefer. It comes with no default styling. It also publishes
an event that can be handled by other code, implementing other flashing
mechanisms.
whitespace gardening
Flash the paste button whenever something is copied.
Merge branch 'discoverable-copy-paste' into testing