Fix inputs provisionned after init

[azorgh]

Hi,

Referred to Issue #39 .

I changed the condition to check if value is empty or not.

[ollwenjones]

These tests are failing because the browsers aren't starting...

[justindujardin]

Please rebase on the latest master to fix the travis build issue for PRs.

[justindujardin]

@pallmallshow I'd like to have a test to cover how this was failing before and see it pass with your changes. Is this something you can do? There is an input test already, so adding another should be a breeze. See: https://github.com/justindujardin/ng2-material/blob/master/test/components/input/input_spec.ts#L73

[sylvaindumont]

The fix work well with data coming from http, but 'undefined' is written in all blanks input.