Implement event stream processing

Adds transparent event stream processing and statistics.
A new 3-tuple trace is introduced as `{Key, Op, Value}`, but
for backwards compatibility `{Key, Val}` implies `=` for `Op`
and `{Key, '*'}` remains as is in the case of wildcards.
A simplified query tree module is generated which reduces
redundant selection conditions to minimize filtering overhead.
Merge branch 'dz-event-stream-processing' of git://github.com/DeadZen/lager into DeadZen-dz-event-stream-processing

Conflicts:
	src/lager_util.erl
Correct the tracing statistics to account for # of installed traces
Pin the goldrush dep to a SHA
Merge branch 'DeadZen-dz-event-stream-processing'