Check the second before the listed date in the headers when verifying signatures.

Due to the signature being calculated before the final date stamp is
applied to the header (thanks requests), we have to check for the
second before the listed date as well before rejecting the signature.
This fixes the occasional BadSignatureError issue that's been occurring.

Signed-off-by: Tyler O'Meara <Tyler@TylerOMeara.com>
Fix some bugs

Signed-off-by: Tyler O'Meara <Tyler@TylerOMeara.com>
Merge pull request #6 from Acidity/feature/fixTiming

Check the second before the listed date in the headers when verifying signatures.