Log Message:
Version 2.7 (released 2011-11-23)

* Verify server signatures per default when a key is provided. The old
behavior can be restored with ykclient_set_verify_signature (ykc, 0);

* Return YKCLIENT_BAD_SERVER_SIGNATURE on missing signature.

Version 2.6 (released 2011-06-06)

* Use fprintf+exit instead of glibc-ism errx.

* Indent code and replace // comments with /* */ comments (for C89).

* Fix dates of releases for 2.4 and 2.5 below (2011 not 2010).

Version 2.5 (released 2011-05-31)

* Implement almost all of Validation protocol 2.0.
The part still known to be missing is parallell querys to all validation
servers using curl-multi.

Version 2.4 (released 2011-03-02)

* Add possibility to supply validation service URL.

* Make Validation protocol 2.0 servers not reject our requests.
They would reject our requests because they did not have a nonce
parameter.

* Add new API ykclient_set_ca_path to set a trusted CA certificates path.

* Fix issue with insecure rpath in the ykclient executable.

* Documentation converted to asciidoc after move to Github.