Fix dependency convergence issue: metrics/slf4j
Removing AsyncAppender in favor of using Logback's AsyncAppender, which doesn't have a dependency on pre-Jetty 9.1's ConcurrentArrayBlockingQueue.
Quote applicationName in SyslogAppenderFactory

When using a user-defined String for the replacement of a regular
expression, we should be quoting it with `Matcher.quoteReplacement`, in
case they use any reserved characters (`/` or `$`).

In this case, we ran in to a problem with a Scala application with a
singleton object for the application, which gets compiled to a class
with a trailing `$`, causing a `StringIndexOutOfBoundsException` here.
Merge pull request #542 from ryankennedy/master

Removing AsyncAppender in favor of using Logback's AsyncAppender, which ...