AGLKVertexAttribArrayBuffer has invalid assertion

[mkurtzsd]

I noticed in this newest version of the AGLK code base, in prepareToDrawWithAttrib:numberOfCoordinates:attribOffset:shouldEnable:, the first assertion changed from count <= 4 to count < 4. This is causing an assertion failure (crash) in my code when attempting to use the buffer to hold a color (GLKVector4) with the attribute GLKVertexAttribColor. In the book, I didn't see any use of this attribute in the examples (or I missed it) so perhaps this change was an oversight.