In practice, pretty much every browser is going to send a default Accept header with a value here.  My goal was to fall back for clients who don't exhibit this behavior, but also to skip expensive parsing if it's clear that the header value is requesting an HTML response (which described the default Accept header for most browsers).  I'm still trying to decide if there's a simpler way to do this - I found that the acceptparse function calls below are *very* expensive per request.

I'm also still considering *removing* this optimization for simplicity and just taking the performance hit - this is a pretty useful feature of pecan that I feel differentiates it a bit, and may be worth the extra expense.