Add killjoy message to the response when > MAX_POINTS

Just like `Buzzkill Mode TM` from the Hipchat karma bot, this prints out
a message explaining the 5 (or MAX_POINTS) limit if someone is giving
(or taking away) more karma.

closes jetpackworkflow#4 the rest of the way

README.md

@@ -18,6 +18,7 @@ API
 * `'taco tuesday'++` - add a point to 'taco tuesday'
 * `++` - add a point to the most previously voted-on thing
 * `thing++ for stuff` - keep track of why you gave thing points
+* `thing+++++++` - adding more than `HUBOT_PLUSPLUS_MAX_POINTS` points will be capped at the max and a `HUBOT_PLUSPLUS_KILLJOY_MESSAGE` will be appended to the updated score.
 * `thing--` - remove a point from `thing`
 * `--` - remove a point from the most previously voted-on thing
 * `thing-- for stuff` - keep track of why you removed thing points

src/mega-plusplus.coffee

@@ -43,6 +43,7 @@ module.exports = (robot) ->
   reasonsKeyword = process.env.HUBOT_PLUSPLUS_REASONS or 'raisins'
   maxPoints = process.env.HUBOT_PLUSPLUS_MAX_POINTS or 5
   reasonConjunctions = process.env.HUBOT_PLUSPLUS_CONJUNCTIONS or 'for|because|cause|cuz|as'
+  killjoyMessage = process.env.HUBOT_PLUSPLUS_KILLJOY_MESSAGE or 'Killjoy Mode™ has enforced a maximum change of ' + maxPoints  + ' points'
 
   # sweet regex bro
   robot.hear ///
@@ -101,6 +102,8 @@ module.exports = (robot) ->
                     "#{name} has #{score} points"
 
 
+      if requestedMagnitude > maxPoints
+        message = message + " (" + killjoyMessage + ")."
       msg.send message
 
       robot.emit "plus-one", {