Merge branch 'obj_mat_file' into 'master'

Fix OBJ material files and face color (Thanks to Sven-Kristofer Pilz for the patch)

closes #20 

See merge request !50
6 jobs for master
Status Name Job ID Coverage
  Test
passed clang-c++11 #3615
Linux

00:22:30

passed clang-c++98 #3617
Linux

00:14:32

passed gcc-c++11 #3614
Linux

00:04:07

passed gcc-c++98 #3616
Linux

00:03:44

passed macos-c++11 #3618
Apple

00:17:15

passed macos-c++98 #3619
Apple

00:08:21