The recommended way to handle colons in completion words
is by using the helper methods:
* _get_comp_words_by_ref with the -n : option
gets the word-to-complete without considering a colon as a word break
removes colon containing prefix from COMPREPLY items
(a workaround for http://tiswww.case.edu/php/chet/bash/FAQ - E13)
Using the helper methods also simplifies the script and
ensures that we get the same behavior on any environment.