Fixes #3: Migrated from MooseX::AttributeHelpers to native Moose traits

Because MooseX::AttributeHelpers is deprecated.
Thanks for pointing it out Karen Etheridge.
Merge pull request #4 from ironcamel/remove-moosex-attributeHelpers

Fixes #3: Migrated from MooseX::AttributeHelpers to native Moose traits