PopupMenu: Add showWithCallback method.
Make compile
Merge pull request #3 from Sciss/master

TreePathSelected documentation and argument names.

Great stuff Sciss, thanks for your contribution!  Sorry for the delay in merging.
Merge pull request #6 from tommycli/master

PopupMenu: Add showWithCallback method, callback on menu hide
Back out pull request #6 because it doesnt compile
Update version to 1.5, small doc changes
Add showWithCallback() based on pull request #7 by tommycli (but in single commit)