dict keys should be sorted before encode

[ttys3]

according to BEP003 http://bittorrent.org/beps/bep_0003.html#bencoding

bencoded dictionary keys MUST be sorted as raw strings, not alphanumerics

Dictionaries are encoded as a 'd' followed by a list of alternating keys and their corresponding values followed by an 'e'. For example, d3:cow3:moo4:spam4:eggse corresponds to {'cow': 'moo', 'spam': 'eggs'} and d4:spaml1:a1:bee corresponds to {'spam': ['a', 'b']}. Keys must be strings and appear in sorted order (sorted as raw strings, not alphanumerics).

see also Frederick888/php-bencode#7
Frederick888/php-bencode#8