Some cleanup to appveyor install step
Some cleanup to appveyor install step

Fix the argument, don't need to use Out-Null anymore to suppress decompression output

Mindtribe/cpputest,asgeroverby/cpputest,cpputest/cpputest,KisImre/cpputest,basvodde/cpputest,offa/cpputest,PaulBussmann/cpputest,offa/cpputest,basvodde/cpputest,basvodde/cpputest,KisImre/cpputest,PaulBussmann/cpputest,offa/cpputest,basvodde/cpputest,offa/cpputest,Mindtribe/cpputest,PaulBussmann/cpputest,KisImre/cpputest,cpputest/cpputest,asgeroverby/cpputest,KisImre/cpputest,asgeroverby/cpputest,PaulBussmann/cpputest,Mindtribe/cpputest,cpputest/cpputest,Mindtribe/cpputest,asgeroverby/cpputest,cpputest/cpputest