Chapter 07 Python on Linux, add `conda` as an alternative

[zhaofeng-shu33]

For "Python Programming Language on Linux" there are many ways to organize the packages. conda is often used in scientific computing community. I suggest mentioning it in the lecture notes as well.

[myl7]

We will consider to add it into the Ch07 supplement chapter. Thanks for your suggestion.

[taoky]

Some contents about conda has been added by #34. There are still some details that can be added in.