Rename vector type.

Refactor file layout of extperimental code.

experimental/multithreaded/README.md

@@ -0,0 +1,16 @@
+# Experimental code for .obj loader.
+
+* Multi-threaded optimized parser : tinyobj_loader_opt.h
+
+## Requirements
+
+* C++-11 compiler
+
+## Compile options
+
+* zstd compressed .obj support. `--with-zstd` premake option.
+* gzip compressed .obj support. `--with-zlib` premake option.
+
+## Licenses
+
+* lfpAlloc : MIT license.