added repetitionInvalidatesBounds to Expression

GitHub issue #5 - PatternSyntaxException: Look-behind group does not have an obvious maximum length
applied more descriptive name to test property

GitHub issue #5 - PatternSyntaxException: Look-behind group does not have an obvious maximum length
added repetitionInvalidatesBounds checks to boundedLength

GitHub issue #5 - PatternSyntaxException: Look-behind group does not have an obvious maximum length
added possiblyZeroLength

GitHub issue #5 - PatternSyntaxException: Look-behind group does not have an obvious maximum length