Exponential distirbution/node rules

[A-Vzer]

I tried implementing the exponential rule however it does not recognize the rule i have created and throws RuleMethodError: no method matching rule for the given arguments even though the rule is clearly (to me) defined.

[bartvanerp]

Thanks for starting this PR. The error was caused because the out.jl file for the Exponential node was not included under prototypes.jl. Hence, the package did not load the rule and therefore for the test it was unknown. I quickly reordered the rules to alphabetical order in the prototypes.jl file for clarity. Please also don't forget to include the test in the runtests.jl file (and possibly reorder these too).

[codecov-commenter]

Codecov Report

Merging #45 (600773a) into master (2bfb1e5) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #45   +/-   ##
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  Coverage   53.40%   53.40%           
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  Files         125      125           
  Lines        3661     3661           
=======================================
  Hits         1955     1955           
  Misses       1706     1706           

Impacted Files	Coverage Δ
src/ReactiveMP.jl	33.33% <ø> (ø)

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[bartvanerp]

@bvdmitri Can we close this PR? I think the exponential mapping will be resolved with the Delta node. If someone needs an Exponential distribution, then we will create an issue later.

[bvdmitri]

@bartvanerp 👍 yes, I think we can close this