Fix description

[xiaokongkong]

1. Fix description

width: list
            number of neurons in each layer. e.g., [2,5,5,3] means 2D inputs, 5D outputs, with 2 layers of 5 hidden neurons.

should be

width: list
            number of neurons in each layer. e.g., [2,5,5,3] means 2D inputs, **_3D_** outputs, with 2 layers of 5 hidden neurons.

Because 3 is in the end of this list

2. remove extra symbols

There are many semicolons in codes, I'm not sure if they are necessary so I removed some. Also, I replaced some redundant symbols like >>> >>>，and replaced them with >>>