Using yarddoc and spring together results in `RuntimeError` for every file

[jferris]

This was pretty hard to track down, and I'm not really sure whose fault it is, but here we go:

In b14e58a, Spring redefines raise on Kernel.

Yard defines methods for all of its tags, such as @param and @raise. It's hard to figure out exactly where this goes wrong, but when Yard tries to invoke raise to generate that tag, it ends up finding Spring's version of the method, which results in the following error for every file:

[error]: Exception occurred while generating 'ClassName.html'
[error]: RuntimeError: 
[error]: Stack trace:
  /path/to/yard/templates/template.rb:355:in `render_section'

The end result is that you cannot use yardoc on Rails projects which use Spring.