Need to make sure compinit is called in the pty or the shell hangs

Only a problem in synchronous mode

The `zsh -f` running in the PTY doesn't know about the non-exported
variables and functions defined in the original shell, thus can't make
suggestions for them. Run local functions in the PTY instead of a new
`zsh` process.

We have to handle things differently based on whether zle is active or
not (async vs. sync mode).

Only need the first completion result

Uses https://github.com/Valodim/zsh-capture-completion with some slight
modifications.

`stty` occasionally hangs (always in CircleCI) inside the async pty.

Disable the tests for now until we can figure out and fix/workaround
this issue.

v0.4.3

For unknown reasons, the pty will occasionally quit running. In these
cases, we still want to remove it so that a fresh one can be created. We
don't actually need this check because error messages from `zle` and
`zpty` are redirected to /dev/null.

One sure way to kill all currently running pty's is to run `exit` in a
subshell. Even without zsh-autosuggestions loaded, the following works:

    % zmodload zsh/zpty
    % zpty -b foo cat
    % zpty -b bar cat
    % zpty
    (31689) bar: cat
    (31666) foo: cat
    % $(exit)
    % zpty
    (finished) bar: cat
    (finished) foo: cat

Issue #188. PR #324.

Thanks to @toadjaune and @IngoHeimbach.

Specific case where this matters is following:

Be in vi insert mode with some text in the buffer and the cursor at the
end of the buffer. Press `esc` to trigger `vi-cmd-mode widget`, then
before the cursor moves (KEYTIMEOUT), press `h` to trigger
`vi-backward-char` widget. When `vi-cmd-mode` original widget exits,
KEYS_QUEUED_COUNT will be non-zero and the suggestion will be lost.

Useful with `binding.pry` to inspect behavior of tests.

closes #328

make Oh my zsh install works without ZSH_CUSTOM defined

Don't fetch suggestions after [up,down]-line-or-beginning-search

These widgets rely on `$LASTWIDGET` being set to restore the cursor
position. When asynchronous suggestions are enabled, and the widget
triggers a suggestion to be fetched, `autosuggest-suggest` will be
called and $LASTWIDGET will be set to it.

Avoid ringing bell when accepting suggestions

`_zsh_autosuggest_widget_accept()` (&al.) passes this function's return status
on, and ZLE rings the bell if it's >0. Not having an original widget isn't an
error condition, so always returning 0 here should be OK to avoid the bell

Fixes #228

v0.4.2

Fixes/support older versions

To support older versions of zsh (< 5.0.8).

We were missing the EXTENDED_GLOB option that allows use of `(#m)` flag.

This reverts commit 7f8ff2867c.

RHEL6 bundles v4.3.11
Ubuntu 14.04 and Amazon Linux bundle v5.0.2

v0.4.1

This fixes a small issue in src/widgets.zsh which makes it so if you
alias [ to g[ (as is done in prezto if the gnu-utility module is loaded)
autosuggestions would fail.

The documentation for GNU test mentions that -o and -a should be avoided
if possible because it's not very clear. Also, with zsh and [[ -o
actually tests if an option is set, which makes this option even more
confusing.

Now that patch has released

Use typeset -g to avoid warnnestedvar warnings

Fixes github issue #271

Simplify escaping of pattern and fix match_prev_cmd strategy

Seems like this would happen on some machines but not on others. Not
sure exactly what's going on, but this is such an edge case I'm just
going to remove the test.

https should work more broadly for folks