Add simple checks

http://markmail.org/message/zlzct6a2ixym24ys

As a general after-the-fact audit, it would be great if the tool could do some basic release checks and include the results in the report. For example verify that all the checksums and signatures included in the dist directory are correct. It would be even cooler if there was some way (perhaps with explicit release metadata) that would link the reported release artifacts to the related vote threads.