fix #833 Widgets cursor position is incorrect

This fixes any <code>TextInput</code> widgets that were suffering from this issue, including:

- [NumberField](http://snippets.ariatemplates.com/samples/github.com/ariatemplates/documentation-code/tree/master/samples/widgets/numberfield "http://snippets.ariatemplates.com/samples/github.com/ariatemplates/documentation-code/tree/master/samples/widgets/numberfield")
- [MultiSelect](http://snippets.ariatemplates.com/samples/github.com/ariatemplates/documentation-code/tree/master/samples/widgets/multiselect "http://snippets.ariatemplates.com/samples/github.com/ariatemplates/documentation-code/tree/master/samples/widgets/multiselect")
- [SelectBox](http://snippets.ariatemplates.com/samples/github.com/ariatemplates/documentation-code/tree/master/samples/widgets/selectbox "http://snippets.ariatemplates.com/samples/github.com/ariatemplates/documentation-code/tree/master/samples/widgets/selectbox")