Don't use @Injector in tests.

I'm frankly unsure why the tests pass with a separate Injector instance as the class methods all still use the Singleton. In any case, this should now protect against any bleed-over between tests as it resets the singleton before each one.

lib/injector.rb

@@ -31,6 +31,10 @@ def method_missing(name, *args)
     def instance
       @instance ||= self.new
     end
+
+    def reset_instance
+      @instance = nil
+    end
   end
 
   def [] (of)

spec/injector_spec.rb

@@ -2,16 +2,16 @@
 
 describe Injector do
   before (:each) do
-    @injector = Injector.new
+    Injector.reset_instance
   end
 
   it 'should blow up if there is no binding for a class' do
-    lambda { @injector[String] }.should raise_error(Injector::NotFound)
+    lambda { Injector[String] }.should raise_error(Injector::NotFound)
   end
 
   it 'should find a class that has used the inject keyword' do
     klass = Class.new { inject }
-    @injector[klass].class.should == klass
+    Injector[klass].class.should == klass
   end
 
   it 'should pass in dependencies' do
@@ -23,7 +23,7 @@
       attr_reader :foo, :bar
     end
 
-    k = @injector[klass]
+    k = Injector[klass]
     k.class.should == klass
     k.foo.should_not be_nil
     k.foo.class.should == dep_foo