Minor cleanups.
Merge pull request #70 from cgay/dev

Minor cleanups.
Fix bugs in http-client discovered by Piotr Klibert:

* $default-http[s]-port shouldn't be the same for client and server, so I
  removed it from http-common and instead use unexported constants in server
  and client.  Client gets 80 and 443, server gets 8000 and 8443.  Eventually
  the client shouldn't need these constants since the uri library should supply
  defaults for schemes that specify them.

* Default read-response-body? to #t in http-request(<string>, <request-method>).

* Use parse-url instead of parse-uri in http-request because
  <base-http-request> expects a <url>.  This may not be the correct long-term
  fix though.  Will look into getting rid of the <url> class completely and
  just have <uri>.
Merge pull request #71 from cgay/client

Fix bugs in http-client discovered by Piotr Klibert
[client] Reduce complexity. Having an <http-request> class and
conversions from that to <base-http-request> just complicates the
code. Also, by changing
  http-request(url, request-method, ...)
to
  http-request(request-method, url, ...)
we can turn ~100 LOC into 5 simple curry statements.
[client] Clean up comments and add TODOs.
[client] Export http-request function
[client] Add some doc.
[client] Send / in request line for empty URI path.  Fixes #2
Merge pull request #72 from cgay/simple-client

Simplify the http-client library
[http-server] Move connection keep-alive handling.

This moves the code from the server's response handling
code to the response's initialize method.
[http-server] Simplify response initialize method.

Remove the direction: keyword argument and validation as it isn't
needed.
[http-server] Just create <request> rather than make it configurable.
[http-server] Collapse some whitespace.