fix(SSHChannelReader): Read output completely before checking command exit.
Merge pull request #260 from calavera/fix_command_channel_reader_race

fix(SSHChannelReader): Read output completely before checking command exit.
fix(signing): Use live ssh-agent for keys
fix(signing): Assign pubkeys directly into array
fix(signing): Create usable PublicKeys for verification
test(functional): Add functional test for signed payloads