word-completion plugin for Tickit::Widget::Entry

 Tickit::Widget::Entry::Plugin::Completion applies code to a
 Tickit::Widget::Entry instance to implement word-completion logic while
 editing. This logic is activated by pressing the <Tab> key.
 .
 If the word currently being edited has a unique match in the list of words,
 then the word is completed entirely, followed by a space.
 .
 If there are multiple words that could complete from the word at the cursor,
 then a popup menu is presented showing the next available characters or
 matches. The user can continue typing more characters to narrow down the
 choice until a unique match is found.