Reverse order of context/frame lookup (issue #119)

[mattbasta]

I don't know if there's any particular reason why contextOrFrameLookup looks at context first, but I think this has been the cause of a lot of heartache surrounding the {% set %} block and also macro arguments. If something in the frame overrides something in the context, the context was still being trusted.

The tests pass for me, as well, which I found both pleasant and surprising.

[jlongster]

I can't remember a specific reason... it may have been out of fear of accidentally clobbering a context value with an internal variable name. But that should never happen, so you're right, it sounds like this should be the right order. We'll just have to see if any issues are files about it in the next release.