Ported Wunderground Service tests

Ported from Kiwi to XCTest.

Two tests have issues though, which is the two that use OHHTTPStubs.h.

Suspect there is a problem with that library with XCode5 and iOS7. Need to investigate next.

Signed-off-by: Ippoippo <ippoippo-software@ippoippo-eco.com>