Ensure "y" character doesn't break "type_keys"

[diogobaeder]

OK, this is not a bug in Pyccuracy, but in Selenium - is recognizes "y" also as a special key, and fires "F10" in firefox during the tests. More info here:
http://jira.openqa.org/browse/SRC-385
For now, in the Mocker branch, I've replaced all the "I slowly type" tests that have the "y" character with other sentences that don't contain it, but this should be fixed sometime.