content: clarify append code example
content: clarify append code example

Rename variable: a (array) -> s (slice).

Capitalize comments to make full sentences.

Simplify printSlice function. There's no need to pass a
descriptive string, since the name of the slice is the same
each time the function is called.

Change-Id: I18981b4c649ee84b121f3aedce5ee62c2fa37b08
Reviewed-on: https://go-review.googlesource.com/19404
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

zorion/go-tour-ca,golians/tour,shuLhan/go-tour-id,golians/tour,scryner/tour,shuLhan/tour,scryner/tour,Go-zh/tour,dupoxy/go-tour-fr,shuLhan/tour,Go-zh/tour,shuLhan/go-tour-id,golians/tour,zorion/go-tour-ca,golang/tour,shuLhan/tour,dupoxy/go-tour-fr,scryner/tour,Go-zh/tour,scryner/tour,Go-zh/tour,shuLhan/go-tour-id,dupoxy/go-tour-fr