Translated
Completed translation of '21-Logging_Slow_Queries' into Spanish. Fix #254.
updated according to feedback
Merge pull request #256 from jcarlosgarcia/efficiency-index-use

Completed translation of "18-Efficiency of index use". Resolves #250
Completed translation of '22-Profiling' into Spanish. Close #255.
Completed translation of '01-Introduction_to_Week4' into Spanish. Close #259.
Minor edits for #254.
Minor edits for #255.
Minor edits for #259.
Merge pull request #257 from puentesarrin/issue-254

Completed translation of '21-Logging_Slow_Queries' into Spanish. Fix #254
Merge pull request #258 from puentesarrin/issue-255

Completed translation of '22-Profiling' into Spanish. Close #255.
Merge pull request #260 from puentesarrin/issue-259

Completed translation of '01-Introduction_to_Week4' into Spanish. Close #259