Adjust flay score

* Remove some duplication with an option extraction helper method.

config/flay.yml

@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 293
+total_score: 296

lib/mutant/helper.rb

@@ -33,5 +33,20 @@ module Mutant
       RUBY_VERSION == '1.8.7'
     end
 
+    # Extract option from options hash
+    #
+    # @param [Hash] options
+    # @param [Object] key
+    #
+    # @return [Object] value
+    # 
+    # @api private
+    #
+    def self.extract_option(options, key)
+      options.fetch(key) do
+        raise ArgumentError,"Missing #{key.inspect} in options"
+      end
+    end
+
   end
 end

lib/mutant/runner.rb

@@ -46,16 +46,11 @@ module Mutant
     # @api private
     #
     def initialize(options)
-      @killer = options.fetch(:killer) do
+      @killer  = Helper.extract_option(options, :killer)
-        raise ArgumentError, 'Missing :killer in options'
+      @pattern = Helper.extract_option(options, :pattern) 
-      end
-
-      @pattern = options.fetch(:pattern) do
-        raise ArgumentError, 'Missing :pattern in options'
-      end
-
       @reporter = options.fetch(:reporter, Reporter::Null)
       @errors = []
+
       run
     end