Added section on the unix philosophy to shell_tools_101

[greyspectrum]

In shell_tools_101.rst in Unix Fundamentals 101, I added a section on "The Unix Philosophy" in response to the Todo note: "Mention that the philosophy here is to have many tools which perform a few discrete tasks, and run them together to get what you want."

My contribution was:

The Unix Philosophy

Unix is characterized by its modular design philosophy. Unix programs are small, single purpose tools that can easily be chained together with other Unix programs. This modular approach allows for a much simpler, more flexible system, since you can combine multiple command line programs to solve a unique problem, without having to write a whole new program to get the job done.

[miketheman]

Thanks! Could you split up the paragraph onto separate lines, per our style guide? https://github.com/opsschool/curriculum/blob/master/meta/style_guide.rst#spacing

[greyspectrum]

Sure thing! Sorry about that. I just pushed another commit to fix the formatting.

[miketheman]

Thanks!