release: 1.3.54

release: 1.3.54

==========

* Bugfix: don't crash on tuplet spanners that don't contain any notes.

* Small cleanup of Dimension_cache: removed a few redundant
fields. Slightly lower memory usage. Dimension_cache is now a `dumb'
struct again.

* Add array index to priority field of text scripts to ensure that
order is unique, and sensible.

* Added an element count statistic.

1.3