Adds feature steps for download of Meter Readings
Improves Usage Point feed builder tests.
Renames FeedBuilderTests to FeedBuilderUsagePointTests
Adds ATOMMarshaller tests for MeterReading
Adds model tests and XML annotations for MeterReading
Adds Feed building for MeterReading
Adds ATOMMarshaller tests for ReadingType
Adds XML annotations for ReadingType
Adds Feed building for ReadingType
Refactors EspiEntry UsagePoint methods into UsagePointEntry
Refactors EspiEntry MeterReading methods into MeterReadingEntry
Refactors EspiEntry ReadingType methods into ReadingTypeEntry
Changes EspiEntry class to be abstract.
Merge pull request #6 from energyos/download-meter-readings

Retail Customer can download Usage Points with Meter Readings and Reading Type