Add changelog

Format is:

    # Version - YYYY/MM/DD
    ## Language
    ### Features
    ### Fixes

Sections should be added as they are needed, so releases don't end up
with empty headings.
Merge pull request #59 from ResourceDataInc/changelog

Add changelog
[skip ci] Add missing c# tests and tweak JSON egs

This introduces test failures for c# that still need to be resolved.
Improve C# IEnumerable implementation
Update IEnumerable return type for JObject values

Return a KeyValuePair<string,dynamic> so the key isn't lost.
Update changelog