准备：
$ curl -O http://python-distribute.org/distribute_setup.py $ python distribute_setup.py
安装：
$ curl -O https://raw.github.com/pypa/pip/master/contrib/get-pip.py $ python get-pip.py
使用：
$ pip install packageName
$ pip search packageName
$ pip install --update packageName
$ pip install --update packageName==version
$ pip uninstall packageName