[#37] Find Weightless Improved

- Works in any mode.
- Finds vertices not belonging to groups AND now vertices with a net
weight of 0.
- Selects the problem vertices.
- Well tested.
[#37] Small Corrections

- Added weight epsilon to account for floating point precision error.
Merge pull request #59 from travnick/feature/fix_weightless

[#37] Find Weightless Improved