ensure-readmes-are-updated: must quote $configlet (#931)
ensure-readmes-are-updated: must quote $configlet (#931)

Otherwise, in the case where `which configlet` has empty output, then
the line `if [ ! -x $configlet ]` is results in `if [ ! -x ]`. Observe
the following:

    $ cat a.sh
    if [ ! -x ]; then
      echo "NOT EXECUTABLE"
    else
      echo "EXECUTABLE"
    fi
    $ sh a.sh
    EXECUTABLE

That means, were $configlet not quoted, configlet not being in the PATH
would mean that the script would proceed (not exit) with $configlet
being empty string. That eventually results in a "generate not found" on
line 38 (which starts with `$configlet generate`).

Compare to:

    $ cat b.sh
    if [ ! -x "" ]; then
      echo "NOT EXECUTABLE"
    else
      echo "EXECUTABLE"
    fi
    $ sh b.sh
    NOT EXECUTABLE

This is the correct behavior, so we must quote $configlet making
"$configlet".
exercism/xhaskell