Get input on the same line as the prompt

Use `System.out.print` over `System.out.println` so that we don't print
a newline after every prompt, meaning you enter input on the same line
as the prompt. Looks much nicer.

Put a space at the end of each prompt line so that entering input on
the same line is fine. You might want to change some of the prompts
to make it a little clearer, though (e.g. appending ": " to indicate
input).