Use multi-dim embed id and sum
Use multi-dim embed id and sum

Conflicts:
	examples/word2vec/train_word2vec.py

wkentaro/chainer,niboshi/chainer,kashif/chainer,rezoo/chainer,cupy/cupy,delta2323/chainer,keisuke-umezawa/chainer,okuta/chainer,wkentaro/chainer,chainer/chainer,tkerola/chainer,chainer/chainer,hvy/chainer,jnishi/chainer,aonotas/chainer,keisuke-umezawa/chainer,cupy/cupy,hvy/chainer,jnishi/chainer,chainer/chainer,niboshi/chainer,niboshi/chainer,ktnyt/chainer,kikusu/chainer,okuta/chainer,wkentaro/chainer,keisuke-umezawa/chainer,ktnyt/chainer,jnishi/chainer,okuta/chainer,jnishi/chainer,ysekky/chainer,anaruse/chainer,okuta/chainer,hvy/chainer,pfnet/chainer,keisuke-umezawa/chainer,cupy/cupy,ktnyt/chainer,kiyukuta/chainer,cupy/cupy,niboshi/chainer,hvy/chainer,chainer/chainer,ktnyt/chainer,wkentaro/chainer,kikusu/chainer,ronekko/chainer