Implement basic task actions API:

* Add Action base class;
* Implement Task::DSL.define_action(keyword, klass);
* Add Task::DSL#actions accessor;
* Apply task DSL actions when Task instances are evaluated.

lib/producer/core/action.rb

@@ -0,0 +1,12 @@
+module Producer
+  module Core
+    class Action
+      attr_accessor :env, :arguments
+
+      def initialize(env, *args)
+        @env        = env
+        @arguments  = args
+      end
+    end
+  end
+end

lib/producer/core/task.rb

@@ -9,7 +9,9 @@ module Producer
       end
 
       def evaluate(env)
-        DSL.new(&@block).evaluate(env)
+        dsl = DSL.new(&@block)
+        dsl.evaluate(env)
+        dsl.actions.map(&:apply)
       end
     end
   end

lib/producer/core/task/dsl.rb

@@ -2,11 +2,23 @@ module Producer
   module Core
     class Task
       class DSL
+        class << self
+          def define_action(keyword, klass)
+            define_method(keyword) do |*args|
+              @actions << klass.new(@env, *args)
+            end
+          end
+        end
+
+        attr_accessor :actions
+
         def initialize(&block)
-          @block = block
+          @block    = block
+          @actions  = []
         end
 
         def evaluate(env)
+          @env = env
           instance_eval &@block
         rescue ConditionNotMetError
         rescue NameError => e