Make Size comparable

Implementation of Size#compareTo(Size) and test cases were imported from Dropwizard.
Make Duration comparable

Implementation of Duration#compareTo(Duration) and test cases were imported from Dropwizard.
Add lower case size units
Add PositiveDurationValidator
Add PositiveSizeValidator
Validate parameters after conversion

Refactored parameter validation to happen after parameter conversion to prevent
duplication of converter logic in validators and to simplify Validator implementations.
Add initial simple Guice support
Add initial Guava support