Add a hook to the 'play' function to allow visualizations.
Merge pull request #58 from PencilCode/playhook

Add a hook to the 'play' function to allow visualizations.
Make readstr show a bigger input box.
Fix a bug in the interaction of jump and fill.

When using a pen fill and lifting the pen, it should allow you to
start a second (disconnected) path.  A typo in the code caused this
to be broken.  Added a unit test that exercises this functionality.
Merge pull request #60 from PencilCode/jumptofix

Fix a bug in the interaction of jump and fill.
Merge pull request #59 from PencilCode/bigreadstr

Make readstr show a bigger input box.
Stop audio when the user interrupts execution.
Fix chord durations.

Regardless of what the standard says, in practice, music found
online in ABC notation appears to count the beats for a stem
according to the shortest duration note within the stem.  This
change implements that defacto rule.
Avoid autoscroll on input widget focus.
Fix play duration heuristic.
Merge pull request #62 from PencilCode/stopaudio

Stop audio when the user interrupts execution.
Merge pull request #63 from PencilCode/focusnoscroll

Avoid autoscroll on input widget focus.
Merge pull request #64 from PencilCode/playduration

Fix play chord duration implementation
More sophisticated ABC notation support.

Support for key signatures, measures with persistent accidentals,
ties, and staccato. For example, the following uses two stacattos
and two ties, to play c# three times and c natural once:

play '^c.cc-|^c.=cc-|c'

Follows the ABC standard: dot before a note is stacatto;
dash after a letter is a tie; vertical bar is a measure bar.
Fix dot tan, cleanup globals.

The tests are now global-clean.
Merge pull request #65 from PencilCode/moreabc

More sophisticated ABC notation support.
Size readstr input box with js instead of flex.
Change test image.

Experiment to see if this reduces flakiness in this test.
Add pause to reduce flakiness.
Merge pull request #66 from PencilCode/readstrfix

Size readstr input box with js instead of flex.