Minisignxml

* Add support for alternative attributes for signing and verifying.
* Fixed verification of signatures using SHA1 as their signature method.
* Updated some dependencies.

* Fix packaging error

* Fixed SHA1 algorithm URIs

* Added `minisignxml.verify.extract_verified_element_and_certificate` to allow specifying multiple certificates when verifying elements to aid certificate rollover.
* `minisignxml.errors.CertificateMismatch` now stores the received certificate and the expected certificates.

* Fixed lxml version selector being too strict.

* Initial release