Improve TextConversionException's error message.
Fix #103: error of RunInstances with NetworkInterfaces
Fix #103: Change type of macaddr in InstanceNetworkInterface.
Add DescribeDhcpOptionsTest.
Add CreateDhcpOptionsTest
Add DescribeSnapshotAttributeTest.
Add CreateSnapshotTest.
ver.0.8.0.0
Add {Create,Delete,Replace}Route