Update stickyHeader width in _renderData function of puidatatable

[StephenCWills]

Ran into issues where the stickyHeader would not resize when the puidatatable's width changed as the result of a scrollbar appearing or disappearing, for instance when the number of rows in the data table changes. This is sort of a blind change to force the stickyHeader to resize every time the data is rendered. There may be a better way.

[StephenCWills]

To replicate, apply "overflow-y: auto" to the style of the div containing the puidatatable. If there is enough data in the table to make the scrollbar appear, the sticky header's width will have been calculated incorrectly.

Here is a jsfiddle demonstrating the issue.
http://jsfiddle.net/staphen/1ez0motc/