Fix for a Fieldset issue, where zero of false values are not populated.

## Issue

When creating forms with the `Fieldset` class, after attempting to populate the fieldset with a model any fields with values inequivalent to false are not parsed.  This is mainly a problem with drop-down fields.

For example:

1 => 'Active',
0 => 'Inactive',

When the value of the field inside the model is ZERO (as stored in the database); I expect `<option value="0" selected="selected">Inactive</option>`  ACTUALLY what I get is `<option value="0">Inactive</option>`.

![mad_kitty](https://f.cloud.github.com/assets/1327452/227678/483297ce-8669-11e2-88b7-7fe4a58b714b.jpg)