Update signature to SHA256

IE issues the following warning upon downloading "The signature of this program is corrupt or invalid." I believe Digiarty may still be using an SHA1 type certificate that is no longer considered secure:

http://social.technet.microsoft.com/wiki/contents/articles/32288.windows-enforcement-of-authenticode-code-signing-and-timestamping.aspx

and

https://dcsoft.wordpress.com/2015/12/14/renew-your-windows-code-signing-certificates-by-december-31-2015/