[Fix: #3786] Sort dictionaries by key in nrepl-bencode

[iarenaza]

CIDER doesn't adhere to Bencode spec which requires dictionary keys to be sorted alphabetically. This hasn't been a problem so far because the bencode reader on nREPL side doesn't validate the order of keys. Still, it will be rigorous to produce correct values according to the selected format.

[Re: #3786]

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Thanks!

If you're just starting out to hack on CIDER you might find this section of its
manual extremely useful.

[bbatsov]

Probably we should mention in the docstring that the keys need to be sorted as per the spec, as this is probably not obvious to people not familiar with bencode - until recently even I didn't know this was in the spec. :D

[iarenaza]

Done!