Support specular highlight, bump, displacement and alpha texture(Remove non-standard "normal map"). Fixes #53.

tiny_obj_loader.h

@@ -26,10 +26,13 @@ typedef struct {
   // illumination model (see http://www.fileformat.info/format/material/)
   int illum;
 
-  std::string ambient_texname;
-  std::string diffuse_texname;
-  std::string specular_texname;
-  std::string normal_texname;
+  std::string ambient_texname;            // map_Ka
+  std::string diffuse_texname;            // map_Kd
+  std::string specular_texname;           // map_Ks
+  std::string specular_highlight_texname; // map_Ns
+  std::string bump_texname;               // map_bump, bump
+  std::string displacement_texname;       // disp
+  std::string alpha_texname;              // map_d
   std::map<std::string, std::string> unknown_parameter;
 } material_t;