Add optional log_root environment variable

Mention the color atom for the formatter config

Fix specification of backend config in log rotation example

add application stop/start suppression for ct logs

Reviewed-by: seancribbs

in common test, starting and stopping applications can make your logs
very noisy.  the patch allows these messages to be suppressed on the
happy path, and raises the high water mark during ct tests so that
messages aren't dropped.

needs log level explicitly set

removed other handlers for common test bounces

Reviewed-by: seancribbs

Add maps support

Fix ct backend dialyzer warnings

Note that compiling on OTP 17.0, or later, will produce beam files
(specifically lager_trunc_io) that are incompatible with R16B03-1, or
earlier, due to erlang:is_map/1 using a new beam opcode (156). However
if compiled on R16B03-1, or earlier, will produce beams files that are
compatible with 17.0, and later, and maps will be formatted where
supported by the active OTP release.

* Fix unmatched return
* Fix set_loglevel call to store mask in state
* Add common_test to plt for ct:pal spec

The example in "Internal log rotation" includes the tuple
{name, "error.log"}

This apparently should be

{file, "error.log"}

as seen in other config examples in README.md.

lager_common_test_backend

fix issue #215: lager.app env overwrites default handlers

the default handlers defined at lager.app overwrites handlers defined previously by application:set_env(lager, handlers, ...) if lager application is started application:start(lager)

Fixed typo in README.md

Fixed forgotten commas.

Added options parameter to lager:trace_file

Fix compile on Release 17 the right way.

Change a latin1 sequence so it is given as a list of integers. this avoids the problem entirely
since ASCII has the same representation in both latin1 and in utf-8

Use a binary rebar compiled with an older version of Erlang.

It has been compiled with R13B03 and resolves issue #183.

Make tests pass on buildbot more of the time

support disable pretty printing records encountered at compile time

Only discard gen_event notifications on high watermark

Previously all messages were being flushed, which meant that trapped exits
and internal gen_event messaging was also flushed, leading to undefined
behaviour.

closes #198

Fix: correct lager startup in crash_log test

Fixed empty tuple bug in lager:pr/2