typeToSheet should contain all supported types

[bryanlalexander]

As noted in Issue #38 a bug was identified where *elbv2.LoadBalancer did not exist in the typeToSheet method causing report generation failure.

All known and supported types should be present in typeToSheet, I have compiled a quick list of items not covered by the typeToSheet method. As the method is being resolved, each type should likely have a test for typeToSheet that verifies at minimum there is no error.

Sheet	Type	Missing
SheetRoles	*iam.Role	False
SheetGroups	*iam.Group	False
SheetPolicies	*iam.Policy	False
SheetUsers	*iam.User	False
SheetBuckets	*s3.Bucket	False
SheetInstances	*ec2.Instance	False
SheetImages	*ec2.Image	False
SheetVolumes	*ec2.Volume	False
SheetSnapshots	*ec2.Snapshot	False
SheetVpcs	*ec2.Vpc	False
SheetSubnets	*ec2.Subnet	False
SheetSecurityGroups	*ec2.SecurityGroup	False
SheetAddresses	*ec2.Address	True
SheetKeyPairs	*ec2.KeyPairInfo	True
SheetStacks	*cloudformation.Stack	True
SheetAlarms	*cloudwatch.MetricAlarm	True
SheetConfigRules	*configservice.ConfigRule	False
SheetLoadBalancers	*elbv2.LoadBalancer	True
SheetVaults	*glacier.DescribeVaultOutput	False
SheetKeys	*helpers.KmsKey	False
SheetDBInstances	*rds.DBInstance	False
SheetDBSnapshots	*rds.DBSnapshot	False
SheetSecrets	*secretsmanager.SecretListEntry	False
SheetSubscriptions	*sns.Subscription	False
SheetTopics	*helpers.SnsTopic	False
SheetParameters	*ssm.ParameterMetadata	False