Switch example application to blog-style application
Add spec to validate fields, and to only run validations on a given field if it is required, or there is a value in the field. Empty, non-required fields are always valid.
Add Base#validate method, with optional field argument to validate a particular field. To be used like:

	<input ng-model="user.name" ng-blur="user.validate('name')">
Update Validations so that:

1) Required validation always runs on required fields
2) Other validations only run if they are also required, or a value is present on the field
3) Custom validations take care of this process
Update user mock to test required/non-required validations
Release 0.1.0