simplifies condition (replaces `is not None`)

Converts sample output reference to relative link

Expands the 'what I learned' section of README

Adds requirements section to README

Resizes console output

Resizes and centers sample output

Crops the console output

Increases quality of the image of sample output

Converts menu option for exit to lowercase

Adds higher quality sample image

Updates sample output to reflect design changes

Adds logic to ensure temperate range is only displayed if min and max values differ

Updates sample output to reflect design changes

Removes unneccesary whitespace after console input

Embeds sample output image in the README