Add seen_table tests

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>
Fix .ycm_extra_conf.py for tests subdir

This adds the libmue dir per -I flag to the build flags so that the
completion works within the tests subdirectory

Signed-off-by: Jan Losinski <losinski@wh2.tu-dresden.de>