Implemented the c:header directive as a Sphinx extension.
Renamed the c_header extension to cheader in keeping with conventions.
Enabled XML output generation in the Doxygen configuration.
Added a documentation dependency on the Breathe extension for Sphinx.

See: https://pypi.python.org/pypi/breathe
See: http://michaeljones.github.io/breathe/
Implemented a simple, homegrown Doxygen XML file parser.
Refactored the Doxygen XML parsing for better code quality.
Removed the Breathe extension for Sphinx.
Implemented Sphinx extensions for documenting the libcpr API.
Added links to the project's Twitter and Tumblr accounts.
Updated Sphinx documentation URLs in the Sphinx configuration file.
Updated all project links to reflect the umbrella organization.