Install package for notebook

[kevinthesun]

In some notebooks, there are some importing modules need to be installed before user can run the notebook. We can: (1) add all those modules as mxnet installation dependencies. This may require system maintainer to frequently update mxnet dependencies when we have new notebooks. (2) Use pip inside notebook to install dependencies while running notebook, This may require notebook writer to identify the modules need to be installed.

@mli @piiswrong

[zihaolucky]

Same question.