Provide vhosts list on Eglide

Summary:
On Grip, a vhosts command offered to read /etc/vhosts.

This is a feature in the users wishlist, as they allow them
to know what IPv6 to use and the associated PTR record.

Test Plan: vhosts

Reviewers: Sandlayth

Reviewed By: Sandlayth

Differential Revision: https://devcentral.nasqueron.org/D816