Merge pull request #81 from rightscale/teal_13_8_acu107842_fix_serializer

acu107842 - Fix Serializer handling of optional second load argument
acu109707 bump agent protocol version to 21 only to distinguish RightLink v5.9 from v5.8
acu109707 add additional note about HTTP-enabled infra agents
acu109707 - Bump gem version to 0.16.1
acu109707 - Removed bogus :environment file
Merge pull request #83 from rightscale/teal_13_09_acu109707_bump_agent_protocol_version_for_v5x9

acu109707 bump agent protocol version to 21 only to distinguish RightLink v5.9 from v5.8