Retry reading from the stream instead of waiting for input data on socket.
Fixed memory leak.
Default timeout handler. Fixed spelling.
Fixed operator to combine flags.
Issue #47: get and fetch messages.

Added a feature to get and fetch a list of messages at the same time,
to avoid a roundtrip to the server.
Premature return if message list/set is empty.
Removed unused/unimplemented function.
IMAP commands.
Modified IMAP parser constructor to make testing easier.
Connection trace facility.
Unit tests for IMAP utils.
Fixed issue #71.