Disable clang for now
Disable clang for now

apparently travis updated to clang 3.3 and that release had broken code coverage

Regression details: http://llvm.org/bugs/show_bug.cgi?id=15953
davidsiaw/luacppinterface,songqing/luacppinterface,davidsiaw/luacppinterface,davidsiaw/luacppinterface,songqing/luacppinterface,davidsiaw/luacppinterface