use buffer passed by callback

when a user types in a command, the associated buffer is not necessarily
the same as returned by weechat.current_buffer (e.g. relay client)
Merge pull request #50 from tribut/current-buffer-nonoptional

use buffer passed by callback (buf argument required)
add [nick] prefix to message

if there is no query buffer, info_get_('irc_buffer') will return the
corresponding server buffer. we need to add a prefix here to avoid
confusion.
Merge pull request #46 from tribut/nick-prefix-buffer

add [nick] prefix to message
More specific mocking for buffer_get_string and info_get.
Wrap long lines.
Use raw string for OTR_QUERY_RE.
Test for adding nick to messages in non-private buffer.
Fix indentation.
support ACTIONs (/me) in otr messages
print a warning when a message was not sent

if require_encryption is set and no otr tunnel is established, give a
warning that the message was not actually sent.
Merge pull request #45 from tribut/action-support

support ACTIONs (/me) in otr messages
Use raw string for regex.
'buffer' is a built-in.
allow smp question and answer to contain non-ascii
fix decoding errors in error messages from potr
Merge pull request #47 from tribut/smp-utf8

allow smp question and answer to contain non-ascii characters
pylint complains about map.

Change to list comprehensions or single calls.
Wrap long lines.
fix typo