Fix case in .boto configuration instructions
Fix case in .boto configuration instructions

[GSUtil], rather than [gsutil].

Also add some markdown formatting.
kivio/PerfKitBenchmarker,msurovcak/PerfKitBenchmarker,meteorfox/PerfKitBenchmarker,gablg1/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,mateusz-blaszkowski/PerfKitBenchmarker,AdamIsrael/PerfKitBenchmarker,lleszczu/PerfKitBenchmarker,askdaddy/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,kivio/PerfKitBenchmarker,ehankland/PerfKitBenchmarker,mateusz-blaszkowski/PerfKitBenchmarker,msurovcak/PerfKitBenchmarker,syed/PerfKitBenchmarker,syed/PerfKitBenchmarker,AdamIsrael/PerfKitBenchmarker,meteorfox/PerfKitBenchmarker,gablg1/PerfKitBenchmarker,askdaddy/PerfKitBenchmarker,ehankland/PerfKitBenchmarker,juju-solutions/PerfKitBenchmarker,ksasi/PerfKitBenchmarker,tvansteenburgh/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,tvansteenburgh/PerfKitBenchmarker,lleszczu/PerfKitBenchmarker,emaeliena/PerfKitBenchmarker,juju-solutions/PerfKitBenchmarker,emaeliena/PerfKitBenchmarker,ksasi/PerfKitBenchmarker