[C++/en] Improve the example

[rilysh]

• [x] I solemnly swear that this is all original content of which I am the original author
• [x] Pull request title is prepended with [language/lang-code] (example [python/fr-fr] or [java/en])
• [x] Pull request touches only one file (or a set of logically related files with similar changes made)
• [x] Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
• [x] If you've changed any part of the YAML Frontmatter, make sure it is formatted according to CONTRIBUTING.md
  • [x] Yes, I have double-checked quotes and field names!

• Changed from using namespace to actually prefix the namespace to avoid conflicts.
• Changes in some areas and comments.

[rilysh]

Hey @mribeirodantas any updates on this? It's been quite a while since I created this PR.

[verhovsky]

@rilysh can you give me push rights to your fork repo https://github.com/mystuffs/learnxinyminutes-docs-2/tree/master so I can update your PR

[rilysh]

@verhovsky Added

Edit: I'm not exactly sure how to give "push rights". Please let me know if this works for you.