upgrade to log4j-2.0-rc2-SNAPSHOT
Shorten the format of properties.

Today its format is
 Properties":[{"name":"some_key","value":"some_value"}]

Since "name" and "value" are erroneous the format can be shorten to
 Properties":[{"some_key":"some_value"}]
the location, logEvent.getSource(), is not always available, eg in the case of async loggers.
Any attempt from LogStashJSONLayout to write location information in this situation results in a NPE.
Merge pull request #7 from finn-no/feature/log4j-2.0-rc2

upgrade to log4j-2.0-rc2-SNAPSHOT
Merge pull request #8 from finn-no/feature/short-properties

 Shorten the format of properties
Merge pull request #9 from finn-no/bugfix/handle-missing-location

Bugfix – handle missing location
off of rc2-snapshot and onto rc2