Draft/outline of spreadsheets (#949)

* Add draft/outline of spreadsheets

* Finish reading from Excel

* Write to Excel + consistency edits

* Add pkgs for writing Excel files

* Release the 🐧s

* Reogranize to highlight tibble/data.frame diffs

* Write again

* Add spreadsheets reference + rename_with janitor

* Move janitor to TO DO in rectangular data

* Need to load tidyverse

* Show csv file

* Add TO DO note

* Use students instead of challenge file in this chp

* Quiet down some of the redundant messages

* Add bit on reading in multiple files

* Fix up students example

* Revert back to old dataset to match spreadsheets chapter

* Fix typos

* Use US spelling

* Comments from Hadley

* Incorporate Hadley's suggestions

Co-authored-by: Hadley Wickham <h.wickham@gmail.com>

data/01-sales.csv

@@ -0,0 +1,8 @@
+month,year,brand,item,n
+January,2019,1,1234,3
+January,2019,1,8721,9
+January,2019,1,1822,2
+January,2019,2,3333,1
+January,2019,2,2156,9
+January,2019,2,3987,6
+January,2019,2,3827,6

data/02-sales.csv

@@ -0,0 +1,7 @@
+month,year,brand,item,n
+February,2019,1,1234,8
+February,2019,1,8721,2
+February,2019,1,1822,3
+February,2019,2,3333,1
+February,2019,2,2156,3
+February,2019,2,3987,6

data/03-sales.csv

@@ -0,0 +1,7 @@
+month,year,brand,item,n
+March,2019,1,1234,3
+March,2019,1,3627,1
+March,2019,1,8820,3
+March,2019,2,7253,1
+March,2019,2,8766,3
+March,2019,2,8288,6

data/students.csv

@@ -0,0 +1,7 @@
+Student ID,Full Name,favourite.food,mealPlan,AGE
+1,Sunil Huffmann,Strawberry yoghurt,Lunch only,4
+2,Barclay Lynn,French fries,Lunch only,5
+3,Jayendra Lyne,N/A,Breakfast and lunch,7
+4,Leon Rossini,Anchovies,Lunch only,
+5,Chidiegwu Dunkel,Pizza,Breakfast and lunch,five
+6,Güvenç Attila,Ice cream,Lunch only,6