improve eval'ing of schedule file to reveal the filename in backtraces

lib/whenever/job_list.rb

@@ -3,21 +3,20 @@ module Whenever
     def initialize(options)
       @jobs, @env, @set_variables, @pre_set_variables = {}, {}, {}, {}
       
-      case options
-        when String
-          config = options
-        when Hash
-          config = if options[:string]
+      if options.is_a? String
+        options = { :string => options }
+      end
+
+      pre_set(options[:set])
+      
+      setup = File.read("#{File.expand_path(File.dirname(__FILE__))}/setup.rb")
+      schedule = if options[:string]
         options[:string]
       elsif options[:file]
         File.read(options[:file])
       end
-          pre_set(options[:set])
-      end
       
-      setup = File.read("#{File.expand_path(File.dirname(__FILE__))}/setup.rb")
-      
-      eval(setup + config)
+      instance_eval(setup + schedule, options[:file] || '<eval>')
     end
     
     def set(variable, value)