add t2.large

* [announcement](https://aws.amazon.com/blogs/aws/new-t2-large-instances/?sc_campaign=launch&sc_category=ec2&sc_channel=SM&sc_content=t2_large_1&sc_detail=std&sc_medium=aws&sc_publisher=tw&adbsc=social_launches_20150617_47668156&adbid=611079737587269632&adbpl=tw&adbpr=66780587)

lib/fog/aws/models/compute/flavors.rb

@@ -44,6 +44,16 @@ module Fog
           :ebs_optimized_available => false,
           :instance_store_volumes  => 0
         },
+        {
+          :id                      => 't2.large',
+          :name                    => 'Micro Instance',
+          :bits                    => 64,
+          :cores                   => 2,
+          :disk                    => 0,
+          :ram                     => 8192,
+          :ebs_optimized_available => false,
+          :instance_store_volumes  => 0
+        },
         {
           :id                      => 'm1.small',
           :name                    => 'Small Instance',