Pieziopop update

Good to see an update for this little app. Here's what's new:

• Song is copied to pasteboard automatically and can be pasted in other audio apps.
• Sent e-mails contain not just the audio file, but also an URL that allows to import and edit the song in piezopop again.
• Choose from five different background colors.
• Insert and remove steps.

The leftmost column is now selectable. The corresponding menu, "+" and "-", allows to insert / remove steps at cursor position. If the cursor is positioned at the first step (top left corner of the song), a selection of background colors is shown instead.
Both functions are somewhat slow, please allow 1-2 sec to take effect.