update to 1.5.16
    
    - Remove everything following a tab (including the tab) from
      hunspell dictionary lines (Resolves: rhbz#1411659)
    - Delete a candidate correctly from the user database even if
      it starts with a prefix to be stripped from tokens (Resolves: rhbz#1411676)
    - Trigger emoji lookup when the input starts or ends with '_' or ' '
    - Better handling of BackSpace and Delete when reaching the
      ends of the preëdit (Resolves: rhbz#1411688)
    - Search for hunspell dictionaries in a list of directories
      (Resolves: https://github.com/mike-fabian/ibus-typing-booster/issues/6)