Allow connection option to be callable

This change allows :connection option to be callable and avoid calling
start on bunny sessions.

lib/sneakers/publisher.rb

@@ -6,9 +6,6 @@ class Publisher
     def initialize(opts = {})
       @mutex = Mutex.new
       @opts = Sneakers::CONFIG.merge(opts)
-      # If we've already got a bunny object, use it.  This allows people to
-      # specify all kinds of options we don't need to know about (e.g. for ssl).
-      @bunny = @opts[:connection]
     end
 
     def publish(msg, options = {})
@@ -29,8 +26,15 @@ def ensure_connection!
 
   private
     def connect!
-      @bunny ||= create_bunny_connection
-      @bunny.start
+      # If we've already got a bunny object, use it.  This allows people to
+      # specify all kinds of options we don't need to know about (e.g. for ssl).
+      @bunny = @opts[:connection]
+      if @bunny.respond_to?(:call)
+        @bunny = @bunny.call
+      else
+        @bunny ||= create_bunny_connection
+        @bunny.start
+      end
       @channel = @bunny.create_channel
       @exchange = @channel.exchange(@opts[:exchange], **@opts[:exchange_options])
     end

lib/sneakers/queue.rb

@@ -19,8 +19,12 @@ def subscribe(worker)
     # If we've already got a bunny object, use it.  This allows people to
     # specify all kinds of options we don't need to know about (e.g. for ssl).
     @bunny = @opts[:connection]
-    @bunny ||= create_bunny_connection
-    @bunny.start
+    if @bunny.respond_to?(:call)
+      @bunny = @bunny.call
+    else
+      @bunny ||= create_bunny_connection
+      @bunny.start
+    end
 
     @channel = @bunny.create_channel
     @channel.prefetch(@opts[:prefetch])