Updated the documentation for R53 HostedZoneCollection to reflect the required use of ID over name

updated the documentation to reflect that you need to use the ID..

In the documentation it shows this example:

\# Find existing hosted zone
r53 = AWS::Route53.new
hosted_zone = r53.hosted_zones['example.com.']

However I found it's more like this:

 r53 = AWS::Route53.new
 hosted_zone = r53.hosted_zones['example.com.']
\# to lookup a route53 hosted zone, you need to use the zone id (i.e hosted_zone.id). It comes as a 14 character string starting with a Z. 
hosted_zone = r53.hosted_zones['ZABCDEFG123456']

I'll admit that I've not dug into the code too much but I don't see any lookups on the param to see if it's a domain or an ID. So i assumed this just a mistake in the documentation. 

Cheers,
Darius