Adjusted code block spacing for improved copy-paste

[hansemro]

Fixes #44

Reference: https://tex.stackexchange.com/a/300132

[hansemro]

Text will be spaced less apart to reduce unwanted space insertion. Maybe this is less readable, but at least this is more reliably copied.

[hansemro]

Specified \lstset{prebreak=\textbackslash} to insert multiline breaks (\) for multiline commands. This will also split long URLs as shown for the wget command without manually inserting multiline breaks.

However, we cannot rely on listings package to always insert breaks in sensible locations (sometimes in the middle of an argument), so I had to manually insert some.

[hansemro]

This should be ready for review.