New tip: Use GET with AJAX requests (ES, EN, PT)

This is a tip based on the information found on [](http://developer.yahoo.com/performance/rules.html).

It's in 3 languages (English, Spanish, Portuguese). English is the original language, Spanish is translated by me (native) and Portuguese is also translated by me (i speak portuguese also) but note that i'm not portuguese, so if anyone around here is portuguese, please check it :).

Hope it helps!
Fran