Ch4: Viz (#77)

* code formatting for viz

* update viz chapter

* updating the viz chapter

* comments addressed through faithful dataset

* more progress on the viz chapter (part way through morley data)

* add back code to create the csv for mauna_loa

* a couple minor typo fixes

* polishing ch4

* minor polish on ch4

* code tags in learning objs

* polish on ch4, fixed number -> percentage in figure labels

* re-added other filetypes...

* better line formatting in saving section

* ignore altair warnings; committed faithful plots

* moved faithful plots to img/

* done polishing ch4

Co-authored-by: Trevor Campbell <[email protected]>

Author: lheagy