SC2207 suggests to use `mapfile` or `read -a`.
`mapfile` was added in Bash 4, while `read -a` only reads the
first line from a file, so both are no go.

Well, since Bash 3 lacks the `readarray` (`mapfile`), kerl's completion does not work - and, unfortunately, Яpple still ships Bash 3 as default shell on macOS.

In this change we directly assign the result of `compgen` to `COMPREPLY` instead of reading the output of `compgen` into a variable.

Tested on:
- 3.2.57(1)-release (macOS default)
- 4.4.23(1)-release (Homebrew)

* wx-20.3: seeing about kerl/kerl/issues/270

* wx-20.3: less failible test + less deps

* wx-20.3: move linux tests out of TravisCI into CircleCI

* wx-20.3: always use git backend (erlang.org is still down)

* wx-20.3: work around fact that erlang.org is down in .travis.yml

* wx-20.3: fix some things

* wx-20.3: looks like skipping happens too late

* Revert "wx-20.3: looks like skipping happens too late"

This reverts commit e0600cefa71760e9bd74e7efc37089d5d75e764e.

* wx-20.3: that should fix it

* wx-20.3: run shellcheck in circle, now travis is only about osx!

* wx-20.3: that did not fix it (cc @mrallen1)

* wx-20.3: shellcheck stable segfaults?

* wx-20.3: should fix shellcheck segfault

* SC1117: Backslash is literal in "\!". Prefer explicit escaping: "\\!".

Not sure about the csh one. @mcrallen1 you have a clue?

* wx-20.3: SC2207: Prefer mapfile or read -a to split command output (or quote to avoid splitting).

* wx-20.3: SC2154: words is referenced but not assigned.

* wx-20.3: replace some double quotes with simple ones

* wx-20.3: ps not found on debian9!?

* wx-20.3: what now

* wx-20.3: lets try a later vsn

* wx-20.3: some cleaning up

* wx-20.3: YAML fun

* wx-20.3: wat

make _get_comp_words_by_ref more strong

Closes #32