Fix bug where headers with arrays would throw a MatchError exception.

[orium]

Apparently header values can be arrays, in which case fs2-rabbit would throw MatchError when trying to convert them to AmqpHeaderVal, which prevented it from consuming messages.

Aparently there are other types that are not supported and will cause the same error: https://www.rabbitmq.com/amqp-0-9-1-errata.html#section_3

[codecov-io]

Codecov Report

Merging #76 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #76      +/-   ##
==========================================
+ Coverage      99%   99.02%   +0.01%     
==========================================
  Files          11       11              
  Lines         101      103       +2     
==========================================
+ Hits          100      102       +2     
  Misses          1        1

Impacted Files	Coverage Δ
...main/scala/com/github/gvolpe/fs2rabbit/model.scala	100% <100%> (ø)	⬆️

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[gvolpe]

Thanks @orium and sorry for the delay in getting back to you, I'm just back from my holidays.

Unfortunately the headers stuff was never fully implemented.