Support new yagnats

Yagnats master deprecated numerous APIs as a result of #78730030. The
new code uses apcera's nats client directly. We'd like to update
loggregatorlib to also use this code path to talk to nats.

[#78730030]
Merge branch 'master' into use-new-yagnats-wrappers
Merge pull request #6 from cloudfoundry/use-new-yagnats-wrappers

Support new yagnats