[shale] clay could catch recursive references

[Ryan Wynn]

I just stumbled upon a problem that clay might be able to catch.

The scenario is that one clay component references a clayJsfid that
includes a reference to an already included clayJsfid.  The result is
a out of memory exception because clay goes into a infinite loop. 
With the nature of clay using a chain context it might be able to
capture a list of already includes clayJsfids and return an error if
there is a duplicate.