Calling a missing yaml partial causes white screen of death without a helpful error message.

[adamjohnson]

Steps to reproduce:

1. Clone housing
2. Start hammer and go to any template.
3. Open your mock data file and try to include a yaml partial like so: <%= YAML::include("does-not-exist.yml") %>

Results:

Internal Server Error
(<unknown>): could not find expected ':' while scanning a simple key at line 23 column 1
WEBrick/1.4.2 (Ruby/2.3.1/2016-04-26) at localhost:2000

Expected Results

Hammer should render a helpful error so the user can troubleshoot and fix the issue. Ideally this doesn't cause a white screen of death.

[zeroedin]

Fixed in 222feb9