Update README.md

#### Install

Pre-requisite:

```

  proper installation of python3

  proper installation of pip

  pip install tensorflow

  pip install keras

  Windows-Ubuntu case: On following error.

  On error: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.22' not found

     sudo apt-get install libstdc++6

     sudo add-apt-repository ppa:ubuntu-toolchain-r/test

     sudo apt-get update

     sudo apt-get upgrade

     sudo apt-get dist-upgrade (This takes long time.)

```     

To install from GitHub, use

    pip install git+https://github.com/haven-jeon/PyKoSpacing.git