Updated README to show new AWS config file format is supported

Updated the README to indicate that the new AWS CLI config file format is also supported, which was added in https://github.com/opscode/knife-ec2/pull/246
Added changes to use public ip address when dns not set in vpc mode
Merge pull request #255 from ClogenyTechnologies/pd/fix-dns-name-not-exists-vpc

[#253] VPC: Server create fails if public IP but DNS hostnames disabled #253
Merge pull request #254 from fletchowns/master

Updated README to show new AWS config file format is supported
Update knife-windows dependency to 0.8.2