The FieldErrorClass was not being set. [Fixes #30]

Allow models created without the 'errors' property to display errors.
Instead of getting the errors object and then checking the
property (`get('errors').get(property)`), just check the property 
(`get('errors.property')`).
Merge pull request #31 from diogomafra/errors-object

The FieldErrorClass was not being set. [Fixes #30]
{{input}} helper with bindings are now recognized in child helpers

Passing bindings to helpers {{inputField}}, {{hintField}} and
{{labelField}} work fine. Hoerver, it is does not when they are passed
to {{input}} helper. Those commits solve this issue. prompt and
placeholder can be passed as bindings for inputField. Tests have been
added and they pass. README has been modified as well.
Version bump to 0.3.2
Revert "{{input}} helper with bindings are now recognized in child helpers"

This reverts commit c255c0567aecd50e80587e20d7ea7eac020e01d2.