example/aws/withContext: Cleanup S3 PutObjectWithContext example (#1167)
example/aws/withContext: Cleanup S3 PutObjectWithContext example (#1167)

Cleans up the S3 PutObjectWithContext example to include more documentation.
zmarois/aws-sdk-go,agworld/aws-sdk-go,calgaryscientific/aws-sdk-go,radeksimko/aws-sdk-go,calgaryscientific/aws-sdk-go,radeksimko/aws-sdk-go,myshen/aws-sdk-go,myshen/aws-sdk-go,myshen/aws-sdk-go,jasdel/aws-sdk-go,myshen/aws-sdk-go,radeksimko/aws-sdk-go,yxd-hde/aws-sdk-go,yxd-hde/aws-sdk-go,zmarois/aws-sdk-go,xibz/aws-sdk-go,calgaryscientific/aws-sdk-go,zmarois/aws-sdk-go,xibz/aws-sdk-go,zmarois/aws-sdk-go,xibz/aws-sdk-go,aws/aws-sdk-go,agworld/aws-sdk-go,yxd-hde/aws-sdk-go,agworld/aws-sdk-go,radeksimko/aws-sdk-go,agworld/aws-sdk-go,yxd-hde/aws-sdk-go,xibz/aws-sdk-go,calgaryscientific/aws-sdk-go