Merge remote-tracking branch 'ztree/master'

1) Fixed bug with where the user unable to delete a file
   or directory
2) Added hotkey 'H' in ztree-diff to toggle between hide/show
   of the ignored files (i.e. starting with .dot)
3) Ignored files do not affect the directory status anymore.
4) Since the new hotkey is added, the version number is increased.

diff --cc packages/ztree/README.md
Simple merge

diff --cc packages/ztree/ztree-diff-model.el
Simple merge

diff --cc packages/ztree/ztree-diff.el
Simple merge

diff --cc packages/ztree/ztree.el
Simple merge