The curl() and curl_download() functions provide highly configurable drop-in
replacements for base url() and download.file() with better performance,
support for encryption (https, ftps), gzip compression, authentication, and
other 'libcurl' goodies. The core of the package implements a framework for
performing fully customized requests where data can be processed either in
memory, on disk, or streaming via the callback or connection interfaces. Some
knowledge of 'libcurl' is recommended; for a more-user-friendly web client see
the 'httr' package which builds on this package with http specific tools and
logic.
