Add info to "troubleshooting" FAQ

[hobovsky]

I can't do this right now, and I don't want to forget:

Troubleshooting FAQ could use some additional bullet points in "confusing tests output" section:

• mismatched line numbers (numbers larger than actual number f lines in solution),
• "actual" and "expected" being swapped in assertion messages,
• add some note on the fact that test output panel can be green while tests actually fail (~~especially on timeout;~~ see https://github.com/codewars/runner/issues/69, check if it still applies).
• Newbies are often confused by JUnit's diff in assertion messages and square brackets present there.

[hobovsky]

Remove information on confusing formatting of bools in C++ (has been fixed with new version of Snowhouse).