Remove pointer to Error so that dynamodb.Error impelents error correctly.
Merge pull request #146 from leelynne/master

Remove pointer to Error so that dynamodb.Error impelents error correctly...
Value is optional and minimum length is 1
Merge pull request #148 from ProTip/master

Value is optional and minimum length is 1
Merge pull request #1 from crowdmob/master

updates from upstream