Update #range-min if low value is adjusted.

[pondermatic]

What was changed

When the slider low value is changed, the #range-min number input is now updated.

Steps to reproduce the issue

1. Reorder a category with many items. On a monitor that is 1920 px wide, I needed at least 82 items.
2. Drag the end of the slider to the right until the start of the slider also moves to the right.

Expected behavior

The request sent to the server should have a start value that is 1 less than the "Post range:" range-min input field.

If the post range range-min displayed value is 5, then the first item displayed should be the 5th item in the category.

Actual behavior

The request sent to the server has start set to the same value as the "Post range:" range-min input field.

If the post range range-min displayed value is 5, then the first item displayed is the 6th item in the category.

The range-min that is displayed to the user starts counting from 1. The get_more_posts ajax action and the _get_order() function start counting from 0.

If items are reordered, the last item is duplicated in the wp_postmeta database table. This causes future reordering attempts to fail and the following error to be sent to the PHP log.
WordPress database error Unknown column 'undefined' in 'field list' for query REPLACE INTO wp_postmeta ...

This fixes issue #12.

This probably addresses review Used to Work.

[pondermatic]

I accidentally committed 47637d1 to this branch instead of another.

[aurovrata]

thanks for this fix.

Reorder a category with many items. On a monitor that is 1920 px wide, I needed at least 82 items.

are you aware that you can extend the grid size by simply reducing the screen resolution (zoom out on the browser (ctrl + mouse scroll) and the plugin will adjust the grid to maintain a perfect square, allowing you to see more posts.