less and grep can't use the preparser

Currently, `less` and `grep` can't take advantage of the preparser (since they're in separate modules). Here's some possible solutions:
1. move `vorpal-less` and `vorpal-grep` into cash
2. move the preparser to a separate module, and allow `vorpal-less` and `vorpal-grep` to require it
3. since glob expansion works for these commands, we could consider moving the preparser code to be right before or right after that.

This should be resolved if `cash` switches over to vorpaljs/bash-parser (since I believe that will handle all the expansion).