Made a couple of changes to the style, so that the extension fits with the theme of RB. 

The header of the extension is dark-grey which matches the heaer title of RB. Also, the body of the extension now is in light-blue which matches the blue colour in header of RB. 

And I added corner bordrs.

Changed the opacity because after I encapsulated the table in a div tag, the opacity doubled.

Changed the width of the input, so that it is centered, with enough padding right and left.

Added more margin on the right, so that the extension is not touching the scrolling bar.
Icons are not used anymore, changed all icons with text.

Remove item button only appears on hover

The over all colors fits better with RB