Imap-tools

* message.MailMessage.attachments now return list of message.MailMessage.Attachment objects

* utils.cleaned_uid_set now not raise ValueError('uid_set should not be empty')
* mailbox.MailBox delete,copy,move,flag,seen methods changed: Do nothing on empty uid_list - return None
* mailbox.StandardMessageFlags renamed to mailbox.MessageFlags

* MailMessage.from_bytes - Alternative constructor

* change license: MIT -> Apache License, Version 2.0
* improve utils.decode_value
* improve MailMessage.attachment decoding
* MailBoxFolderManager.status now returns int values in result
* fix query builder bugs - imap prefix notation rules
* query builder: The key types are marked with `*` can accepts a sequence of values like list, tuple, set or generator.
* add new examples

Added query builder - implemented the search logic described in rfc3501
MailBox.fetch - added "charset" parameter
If the "charset" argument is specified in MailBox.fetch, the search string will be encoded to this encoding.
MailMessage.date now returns datetime.date
MailMessage.date_str attribute added
MailMessage.headers attribute added
MailMessage.id removed
ImapToolsError base exception class removed
MailBoxWrongFlagError exception class removed
functions: (cleaned_uid_set,check_command_status,decode_value,parse_email_address,parse_email_date,quote,pairs_to_dict)
moved to utils module
readme text improved
fixed folder.set encoding dug

Add context manager