update docs to reflect security group changes when booting instances

README.rdoc

@@ -25,6 +25,10 @@ You'll get reminded that things are missing.
 So just add the missing stuff and you are off to the races:
 
   server = AWS.servers.create(:image_id => 'ami-5ee70037')
+  # you might also want a security group, which would go more like this:
+  # AWS.servers.create(:image_id => 'ami-5ee70037', :group => ['secure'])
+  # NOTE: currently you can only have one group at boot time, so the first
+  # element of the array will be used (and the rest will be disregarded)
 
 But don't forget to cleanup or you'll regret it when you get the bill:
 

lib/fog/aws/requests/ec2/run_instances.rb

@@ -21,7 +21,7 @@ unless Fog.mocking?
         #   * 'Placement.AvailabilityZone'<~String> - Placement constraint for instances
         #   * 'DeviceName'<~String> - ?
         #   * 'Encoding'<~String> - ?
-        #   * 'groupId'<~String> - Name of security group for instances
+        #   * 'SecurityGroup'<~String> - Name of security group for instances
         #   * 'InstanceType'<~String> - Type of instance to boot. Valid options
         #     in ['m1.small', 'm1.large', 'm1.xlarge', 'c1.medium', 'c1.xlarge', 'm2.2xlarge', 'm2.4xlarge']
         #     default is 'm1.small'