[shell] Remove inline comment

`stat` does work on Mac OS X, but it uses a different syntax¹. However,
in this particular case, `wc -c` remains the best solution.

¹ fileSize=$( stat -f"%z" "${tmpFile}" 2> /dev/null;        # OS X \
              stat --printf="%s" "${tmpFile}" 2> /dev/null  # GNU )
[vim] Add `cr` (calculate result) key mapping

Make vim use the `cr` key mapping to perform simple calculations and
insert the result into the document (e.g.: `5*5=` + ,cr => `5*5=25`).

Ref: http://vimcasts.org/episodes/simple-calculations-with-vims-expression-register/