Cannot preview themes with Mock Builder VM

[adamjohnson]

Steps to reproduce the issue

1. Clone the mock-builder-vm repo, cd to it and vagrant up to build the machine.
2. Go to localhost:2000/some-theme/index.rhtml

Results

Internal Server Error

cannot load such file -- mock.rb
WEBrick/1.3.1 (Ruby/1.9.3/2014-11-13) at localhost:2000

http://cl.ly/aKKb

Expected results

It should load and preview a theme built for Slate 1.

Environment

1. OSX Yosemite.
2. All browsers.

Support details: http://cl.ly/aJet