upgrade sklearn pip code example

Example 1: sklearn version

import nltk
import sklearn

print('The nltk version is {}.'.format(nltk.__version__))
print('The scikit-learn version is {}.'.format(sklearn.__version__))

# The nltk version is 3.0.0.
# The scikit-learn version is 0.15.2.

Example 2: conda install sklearn

python3 -m venv sklearn-venvpython -m venv sklearn-venvpython -m venv sklearn-venvsource sklearn-venv/bin/activatesource sklearn-venv/bin/activatesklearn-venv\Scripts\activatepip install -U scikit-learnpip install -U scikit-learnpip install -U scikit-learnpip3 install -U scikit-learnconda create -n sklearn-envconda activate sklearn-envconda install scikit-learn