Fix failing spec where .set("html") should accept an array with values.
Fixes #2402 for 1.2. Overwrite String contains with the MooTools version.

Firefox 18 implements .contains, and ES6 might do that as well. That breaks
some stuff, so we have to make sure it's overwritten with the 'correct'
MooTools version.
Update specs
Merge pull request #2462 from arian/1.2x

Fixes for 1.2.6