switch to maven from sbt
simplified appender
improved null checking
add some basic tests
Various bug fixes

- Add a public constructor to RollbarAppender
- Remove logging from NotifyBuilder
Updates to the servlet filter and JSON builder

It doesn’t look like the existing servlet support was functional. The
servlet-api dependency is now optional.
added servlet filter test
Rename package and update docs
Fixed readme typo
Add travis config
Added Travis-CI button
Remove logback from package name
Updated pom
add sonatype to distro management
add release profile to pom
Fix for header and param MDC parsing
Extra error checking on config
Updated the example
Add support for a static rollbar context
message -> formattedMessage

Use the formatted message instead of the raw message for the rollbar
message element.