Hex Wings - Solid end and grips bit

Remixed from walter's model here: https://www.thingiverse.com/thing:767711

Changes made:
* Added a solid end to stop the bit from sliding through the handle. Means you can apply downward force on a screw.
* Tapered the Hex bit towards the base of the hole so it grips the bit and holds it. Bit doesn't fall out when turned up-side down.
* Flattened the sides to it takes up less space and lies flat in a toolkit.