set $wgLanguageCode in travis to something non-english

quite a few tests currently make the assumption
that $wgLanguageCode = 'en'. If the wiki where the tests run
has it set to something else, then a bunch of tests fail.

Change-Id: Ic83d2dc4ded370e3bb5ddc6f57ac0e40e33f3b42
Merge "set $wgLanguageCode in travis to something non-english"