Fix BOOST_ROOT env. var. in appveyor
Fix BOOST_ROOT env. var. in appveyor

BFH-E1D-2015-2016/SuperTeacher,LarsAeschlimann/SuperTeacher,NicoHaui/SuperTeacher,LarsAeschlimann/SuperTeacher,BFH-E1D-2015-2016/SuperTeacher,NicoHaui/SuperTeacher,NicoHaui/SuperTeacher