More resilient lookup

To improve the user experience:
- on queries of non-existent emotes, fall back to a default
  instead of returning KeyError
- allow lookup of emotes regardless of capitalization

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

plugin.py

@@ -160,7 +160,9 @@ class UnicodeEmoji(callbacks.Plugin):
         Prints the Unicode emoji as listed here https://gist.github.com/mogad0n/476c3880dc0e0a059ed03efa265e50f7
         """
 
-        re = emoji[emote]
+        re = emoji.get(emote.lower())
+        if re is None:
+            re = emoji['fuck-off']
         irc.reply('%s' % re, msg=msg, prefixNick=False )
 
     e = wrap(e, ['text'])