Make colortbl parsing more robust

[zoehneto]

This PR fixes #81.

@MooDySmiles could you please test whether this change fixes your problem?

[coveralls]

Pull Request Test Coverage Report for Build 232

• 8 of 11 (72.73%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 68.079%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/rtfjs/parser/destinations/ColortblDestinations.ts	8	11	72.73%
<!--	Total:	8	11	72.73%	-->

Totals
Change from base Build 230:	-0.01%
Covered Lines:	3227
Relevant Lines:	4470

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💛 - Coveralls

[MooDySmiles]

Works like a charm! Thanks you! When are you planning on release this?

[zoehneto]

I'll merge the PR now and then create a new release