Feature Request: Permit multiple coverage formats per language

[bencooper222]

I noticed that you support most coverage formats but basically only 1 per language. I was wondering if you'd be able to change that. Javascript's primary test coverage tool (Istanbul) supports basically every format under the sun and it'd be nice to be able to not use lcov with CodeClimate.

The specific issue at hand is that Istanbul isn't a well-funded project so errors like this one that completely break its ability to generate lcov.info can cripple Javascript test coverage and stick around for a while.