migration required before Sept. 1 - 2014

[jfromaniello]

This pull request include some changes needed before September 1 - 2014 as explained here:

https://developers.google.com/+/api/auth-migration#timetable

Please also notice that I've added the default scope to profile so we don't break existing examples and documentation.

I've also added some warns that might be useful for some folks using this library.

Thanks

[codeactual]

Thanks for kicking this off. I think there might be two more changes to make:

1. I think Strategy.prototype.userProfile in lib/passport-google-oauth/oauth2.js needs one more change: "profile.emails = json.emails;".
2. Try replacing 0.4 with 0.10 in .travis.yml to fix the current build error.

[jfromaniello]

Also we should make clear that now you have to enable Google+ API in the api console otherwise it works the first time but not on subsequent calls

[jaredhanson]

Merged with changes described in #66. Thanks!

[jfromaniello]

Thanks to you man, :)