Fixed bug (fixed two links on the same line)

Fixed incorrect conversion of the following two links on a line:

Hopefully this review will help those on the fence find a game they love, too. If you play the game for the first time, you might find the [official rules videos](https://www.youtube.com/playlist?list=PLMJm0S_nwuBU-TDn7PSrGhwMfkaRXBQGV) useful. Also, don't forget to check out Scott's [advice for new players](https://boardgamegeek.com/thread/3381676/teaching-the-game-to-noobs-including-yourself)!

(the link was extracted as everything between the first and the last parenthesis).

Added tested conversion examples (in Tests/).

Simpler code. Improved documentation.

Maximum header level increased to 3

Level-3 headers are now handled too.

Additional Markdown handled

This version is inspired by issue #1 and adds:

• underline,
• strikethrough,
• monospaced code.