Merge pull request 84

[sharwell]

This pull request resolves the conflicts to merge #84.

[SergeyTeplyakov]

👍

[thomas-delahaye]

Unfortunately, the contracts for IDictionary<TKey, TValue>.ContainsKey and the like might not be correct for all implementations. The MSDN site for IDictionary<TKey, TValue> says in the remarks "Implementations can vary in whether they allow key to be null."...
The same applies to Add(TKey, TValue) and Item[TKey] (but no remarks for Remove(TKey) and TryGetValue(TKey, out TValue)...).

[sharwell]

@thomas-delahaye Can you create a separate issue for that? This PR is merged and treated as effectively "closed", but I don't think we should lose track of your findings. (and I'm really sorry about the delay in responding!)