Rework logic to remove confusion; add comment about why modifier keys are ignored.
Merge branch 'feature/chatbox-history'
Merge pull request #195 from mjtko/feature/chatbox-history

Add 'history' capability to the chatbox input
Preview emojis in chatbox.
Merge remote-tracking branch 'upstream/master'
Remove MP3 files (not currently supported in Firefox or Opera); added threetone-alert.wav to replace gong.mp3 for mention sounds; updated music_player to remove references to unused/obsolete MP3s.
whitespace is significant in messages, so don't put any in that we don't need.
Same whitespace issue for user notification; use 'System message' rather than 'Kandan bot'
Improvements to atwho regexes to only match at start of line or after whitespace.