Update README.md

update cordova hello world link to https://github.com/apache/cordova-app-hello-world
Merge pull request #56 from netalex/patch-1

[doc] Update URL reference to cordova-app-hello-world.
[#43] Guidance added to config.xml
[#43] Reformat the config.xml comments.
[#43] Use current version of PhoneGap.