Fix  call to make-header so that it sets the header argument
Set resource types for :500 and :400 resources.
Add some error checking to extract-req function.  now returns nil if
the client closes the connection without transmitting a request, or
returns a :500 request if an exception occurs.

Need to differntiate between "client made an error" and "server made
an error" still..
Have :500 request-method use the resource :500
Handle exceptions when writing to stream. (e.g. pipe broken / socket
closed)
Merge branch 'master' of https://github.com/cniles/lehs