Fix 0.4 error, use keys to check in dict
Fix 0.4 error, use keys to check in dict

ERROR: LoadError: Associative collections only contain Pairs;
Either look for e.g. A=>B instead, or use the `keys` or `values`
function if you are looking for a key or value respectively.

JuliaPackageMirrors/Lexicon.jl,MichaelHatherly/Lexicon.jl,hayd/Lexicon.jl