Add `:wrap` to --preview-window to wrap lines instead

Close #756

Close #357
Close #738

    TAGS=tcell make install

    printf "\x1b[38;2;100;200;250mTRUECOLOR\x1b[m\n" |
        TERM=xterm-truecolor fzf --ansi

    : | fzf --preview 'echo foo'

To build fzf with ncurses 6 on macOS:

    brew install homebrew/dupes/ncurses
    LDFLAGS="-L/usr/local/opt/ncurses/lib" make install

Also reduce the default delay to 50ms. We should not set it to 0ms as it
breaks escape sequences on WSL. If 50ms is not enough, one can increase
the delay by setting $ESCDELAY to a larger value.

Also add support for alt-[0-9] and f1[12]

`-fstype dev` is invalid. It's devfs on macOS and devtmpfs on Linux.

The updated regular expression should include not all but most of the
frequently used ANSI sequences. Close #735.

Close #732

Minor README markup fix

Close #661

- Fix display of CJK wide characters
- Fix horizontal offset of header lines
- Add support for keys with ALT modifier, shift-tab, page-up and down
- Fix util.ExecCommand to properly parse command-line arguments
- Fix redraw on resize
- Implement Pause/Resume for execute action
- Remove runtime check of GOOS
- Change exit status to 2 when tcell failed to start
- TBD: Travis CI build for tcell renderer
    - Pending. tcell cannot reliably ingest keys from tmux send-keys

`TAGS=termbox make` (or `go build -tags termbox`)

Close #726

This reverts commit 02c6ad0e.

https://github.com/junegunn/fzf/issues/391#issuecomment-257090266

e.g. fzf --preview 'printf "$(tput setaf 2)foo$(tput sgr0)bar\nbar\n"'

Close #722