add reselect-Visual - vim's 'gv'

Hi,
  I'm looking to add vim's 'gv' functionality. Currently it handles a selection turned off by 'v', 'V' and 'y'.  I'm looking for feedback. If this looks good, I'm happy to add a test and implement this additional bit of gv:
```
 After using "p" or "P" in Visual mode the text that
 was put will be selected.
```
Thanks for your awesome editor! I'm currently using it from LightTable