Fix for #43. Excape double quotes in credentials.

[erikhh]

This should fix #43

Normally I would have preferred to use Guava's Escaper class for this. But it was only available somewhere deep in the shaded part of Freebuilder and I didn't want to add an extra dependency for just this. So I opted for slightly less extensible manual option.

[devshawn]

Awesome -- thank you very much for the fix, @erikhh! I appreciate you not adding another dependency -- I'm happy with the manual function.

[akabanov]

Don't want to be that guy, but what about escaping the escape character? :)
I'm just currently fixing the same issue in my project and lucky to already have org.apache.commons.text.StringEscapeUtils#escapeJava in the dependencies which works like a charm.

[erikhh]

@akabanov I think the most effective way to get your point across is submitting a new PR with the proposed changes.