[es] Update chapter 3: fixed markdown mistake

Fixed wrong character to indicate markdown span of code:
There was made with apostrophes instead of backtick quotes

Signed-off-by: Carlos Arturo Guerra Parra <carlosarturoguerra@gmail.com>
[es] Update chapter 3: fixed some mistakes

* Suspension points had 4 or 5 points instead of 3.
* Closing exclamation mark not opened.
[es] Fixed some orthography mistakes
Merge pull request #763 from mesjetiu/es_chapter_3

[es] chapter 3: Fixed some mistakes