fix colon with emoji problem

lib/rumoji.rb

@@ -14,7 +14,7 @@ module Rumoji
 
   # Transform a cheat-sheet code into an Emoji
   def decode(str)
-    str.gsub(/:(\S?[\w-]+):/) {|sym| Emoji.find($1.intern).to_s }
+    str.gsub(/:([^s:]?[\w-]+):/) {|sym| Emoji.find($1.intern).to_s }
   end
 
   def encode_io(readable, writeable=StringIO.new(""))

spec/rumoji_spec.rb

@@ -25,6 +25,10 @@ describe Rumoji do
       Rumoji.decode(":poop:").must_equal @poop
     end
 
+    it "transforms a cheat-sheet code into an emoji with colon" do
+      Rumoji.decode("::poop:").must_equal ':' + @poop
+    end
+
     it "transforms a cheat-sheet code with a dash into an emoji" do
       Rumoji.decode(":non-potable_water:").must_equal @non_potable_water
     end