onwards to 0.8.8.7

Signed-off-by: Riccardo Spagni <ric@spagni.net>
revert the removal of the 'arch' flag from the release-static target
added gpg key for warptangent

Signed-off-by: Riccardo Spagni <ric@spagni.net>
Merge branch 'master' of https://github.com/fluffypony/bitmonero