update input options (#10)

* restructure docs

* update doc

* update requirements, make output optional arg

* fix formatting

* update input options

doc/input.md

@@ -8,9 +8,9 @@ The program options can be displayed by running
 This will return the possible input options and type of parameters. 
 
 For example, to calculate the side length of a square with the same area as a circle of radius r, you would run  
-`python ./src/main.py square -r 4`  
+`python ./src/main.py -o square -r 4`  
 
 For the side length of a pentagon, you would provide  
-`python ./src/main.py square -r 4`  
+`python ./src/main.py -o pentagon -r 4`  
 
 The program will then return the side length of the selected object.