Don't trigger ClosingBraceRule across line breaks

[joshfriend]

Closes #592

[jpsim]

Thanks! Could you please add regression tests in nonTriggeringExamples and triggeringExamples?

[joshfriend]

Added! I didn't realize those were test cases...

[jpsim]

Thanks for the tests, looks good now!

I didn't realize those were test cases...

That's described a bit in the rules section of our CONTRIBUTING.md document:

All new rules or changes to existing rules should be accompanied by unit tests.

Whenever possible, prefer adding tests via the triggeringExamples and nonTriggeringExamples properties of a rule's description rather than adding those test cases in the unit tests directly. This makes it easier to understand what rules do by reading their source, and simplifies adding more test cases over time.