Fix sink name typo in docs

Reviewed-by: macintux

Ensure traces pointed to files work in config file

Reviewed-by: macintux

Flappy test clean up for TravisCI

Reviewed-by: macintux

Export configure_sink/2 for runtime sink config

Reviewed-by: macintux

Address #286. This will enable applications to
dynamically configure log sinks, provided they
have already instrumented the code via parse
transformation to use those sinks.

Addresses #287

Update travis yml

Put the warning map value into process dictionary (Fix OTP 18 test failures)

Address #332: try both id and name

Leverage existing lager_app:get_env wrapper for error_logger_lager_h

The sync_error_logger file looks up the value to send from a process
dictionary entry named `warning_map' When it is unset, it uses a mapping
which is fine for OTP 17 and before, but 18 and 19 the value changed.

So now we put the current mapping value into the process dictionary so
that the messages do not cause failed tests.

Port improper iolist support from io_lib_format.erl & add tests

Reviewed-by: macintux

API to explicitly call log rotation

Reviewed-by: macintux

Do not add logroot in expand_path sometimes

Reviewed-by: bsparrow435

Option to not reformat error_logger messages

Reviewed-by: macintux

If expand_path/1 already contains LogRoot in its RelPath, do not
add it again.

Close file right after rotation

Reviewed-by: bsparrow435

Start traces after extra sinks are started

Reviewed-by: macintux

Bump goldrush to 0.1.8 for not equal filters

Reviewed-by: macintux

Fix internal tuple argument order

Reviewed-by: macintux