tell.coffee: Use current recipient name

Address the recipient by his current username when delivering messages. As prefix matching is applied to recipients' names, it is  insufficient to address the user by the prefix, as their client most likely will not issue a highlight this way.
Update mention regex to match @org/team correctly
Filter out mentions with more than one forward slash
Support whats|what is|what's
youtube-info.coffee: Add missing - and _ to short URL match
Merge pull request #1187 from driverdan/master

Add missing - and _ to short YouTube URL match
Merge pull request #1171 from spajus/patch-1

GitHub Pull request notifier: Update mention regex
Merge pull request #1186 from wadewilliams/patch-1

Support whats|what is|what's
Adjusting CAH to use respond instead of hear
Merge pull request #1190 from nwest/cards-against-humanity

Adjusting CAH to use respond instead of hear
Fix regular expression in plusplus script to properly match umlauts

The previous regular expression would not correctly match inputs like "Björn ++" or "Björn --", because it expected a group of word-characters or whitespace-characters followed by a group of non-word-characters or non-whitespace-characters.

With this fix the regular expression now expects a group of word-characters or non-space-characters followed by a group of non-word-characters or space-characters.
Merge pull request #1197 from benedikt/patch-1

Fix regular expression in plusplus script to properly match umlauts
Merge pull request #1156 from lorenzhs/patch-1

tell.coffee: Use current recipient name