httr 0.5

You can now save response bodies directly to disk by using the write_disk()
config. This is useful if you want to capture large files that don't fit in
memory (#44).
Default accept header is now "application/json, text/xml, /" - this should
encourage servers to send json or xml if they know how.
httr_options() allows you to easily filter the options, e.g.
httr_options("post")
POST() now specifies Curl options more precisely so that Curl know's
that you're doing a POST and can respond appropriately to redirects.

Caching

Preliminary and experimental support for caching with cache_info() and
rerequest() (#129). Be aware that this API is likely to change in
the future.
parse_http_date() parses http dates according RFC2616 spec.
Requests now print the time they were made.
Mime type application/xml is automatically parsed with ``XML::xmlParse()`.
(#128)

Now possible to specify both handle and url when making a request.
content(type = "text") uses readBin() instead of rawToChar() so
that strings with embedded NULLs (e.g. WINDOWS-1252) can be re-encoded
to UTF-8.
DELETE() now returns body of request (#138).
headers() is now a generic with a method for response objects.
parse_media() failed to take into account that media types are
case-insenstive - this lead to bad re-encoding for content-types like
"text/html; Charset=UTF-8"
Typo which broke set_cookies() fixed by @hrbrmstr.
url_ok() works correctly now, instead of always returning FALSE,
a bug since version 0.4 (#133).