[MdTable] Sort by ID failing

[SirNeural]

Steps to reproduce

Create a table that can be sorted, and attempt to sort an md-numeric row.

Which browser?

Vue-Material@1.0.0-beta-7
Vue@^2.5.0
Electron@1.7.10

What is expected?

ID's should be sorted in order of ascending or descending depending on user input

What is actually happening?

ID's column is not getting sorted at all, no changes are made to the order of the columns. I think there may be missing logic to sort by numerical value instead of lexicographical value?

Reproduction Link

https://codepen.io/anon/pen/RxKMxW
Sort by name, and then attempt to sort by id, nothing changes