Improve lager_syslog_backend to support non-atom output log levels.

This supports forms such as "!notice" for configuring the output
log level (using the config handling changes from 7aa316902e2d in
lager).
Merge pull request #9 from ewanmellor/non-atom-levels

Improve lager_syslog_backend to support non-atom output log levels.
updated readme for clarity
amended riak_info to riak as requested
Merge pull request #10 from basho/update_readme

updated readme for clarity
Roll version 2.0.2
Merge branch 'master' into 2.0
Roll version 2.0.3