Lowered Bone matrix array in vertex shader to 251 to avoid software rendering in OSX
Added warning to README.md about performance issue in OSX
(doc) fix Japanese in CONTRIBUTING.md

日本語的に微妙におかしい点を修正しました。
Change VMDInfo to use vectors instead of C-style arrays
Remove '___Count' variables from VMDInfo structs (use vector's size() func instead)
Remove 'Vocaloid Motion 0002' string from VMDInfo struct (no need to store in memory
Add VMD file-writing function