vadyalex

I might be interested in helping to refactor to newer MongoDB Java API as well as general Monger maintenance.

I got a feeling I would like to have `_map_by_key` once or twice recently.. Re-iterating my thoughts I identified the root cause for myself is why would I want to...

Even though I would say _improper design_ of `Response` rather than _improper use_ adding _"Vary: Accept-Encoding"_ to the response object even if it's already there is a bug.

Note that _Jersey 2.0_ shares my train of thought - **do not add if it's already there**. Refer to correspondent [code](https://github.com/jersey/jersey/blob/master/core-server/src/main/java/org/glassfish/jersey/server/filter/EncodingFilter.java#L110-110).