httr 0.4

New features

• New headers() and cookies() functions to extract headers and cookies
  from responses. Previoulsy internal status_code() function now exported
  to extract status_code() from responses.
• POST(), PUT(), and PATCH() now use encode argument to determine how
  list inputs are encoded. Valid values are "multiple", "form" or "json".
  The multipart argument is now deprecated (#103). You can stream a single
  file from disk with upload_file("path/"). The mime type will be guessed
  from the extension, or can be supplied explicitly as the second argument to
  upload_file().
• progress() will display a progress bar, useful if you're doing large
  uploads or downloads (#17).
• verbose() now uses a custom debug function so that you can see exactly
  what data is sent to the server. Arguments control exactly what is included,
  and the defaults have been selected to be more helpful for the most common
  cases (#102).
• with_verbose() makes it easier to see verbose information when http
  requests are made within other functions (#87).

Documentation improvements

• New quickstart vignette to help you get up and running with httr.
• New api-packages vignette describes how best practices to follow when
  writing R packages that wrap web APIs.
• httr_options() lists all known config options, translating between
  their short R names and the full libcurl names. The curl_doc() helper
  function allows you to jump directly to the online documentation for an
  option.

Minor improvements

• authenticate() now defaults to type = "basic" which is pretty much the
  only type of authentication anyone uses.
• Updated cacert.pem to version at 2014-04-22 (#114).
• content_type(), content_type_xml() and content_type_json() make it
  easier to set the content type for POST requests (and other requests with
  a body).
• has_content() tells you if request has any content associated with it (#91).
• Add is_interactive() parameter to oauth_listener(), init_oauth1.0() and
  init_oauth2.0() (#90).
• oauth_signature() and oauth_header() now exported to make it easier to
  construct custom authentication for APIs that use only some components of
  the full OAuth process (e.g. 2 legged OAuth).
• NULL query parameters are now dropped automatically.
• When print()ing a response, httr will only attempt to print the first few
  lines if it's a text format (i.e. either the main type is text or is
  application/json). It will also truncate each line so that it fits on
  screen - this should hopefully make it easier to see a little bit of the
  content, without filling the screen with gibberish.
• new_bin() has been removed: it's easier to see what's going on in
  examples with httpbin.org.

Bug fixes

• user_agent() once again overrides default (closes #97)
• parse(type = "auto") returns NULL if no content associated with request
  (#91).
• Better strategy for resetting Curl handles prevents carry-over of error
  status and other problems (#112).
• set_config() and with_config() now work with tokens (#111).