Make RSS valid

[j0k3r]

Validation failed with the previous feed (even if I checked it ..)
http://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fgraphql.org%2Fblog%2Frss.xml

Following #40

This feed does not validate.
    line 1, column 38: Missing namespace for feed [help]
    <?xml version="1.0" encoding="utf-8"?><feed><title>Blog | GraphQL</title><li ...
                                          ^
    line 1, column 112: Missing feed element: id [help]
    ... ><link href="http://graphql.org/blog/"/><entry><title>Wrapping a REST AP ...
                                                 ^
    line 1, column 112: Missing feed element: updated [help]
    ... ><link href="http://graphql.org/blog/"/><entry><title>Wrapping a REST AP ...
                                                 ^
    line 1, column 263: id must be a full and valid URL: /blog/rest-api-graphql-wrapper/ (4 occurrences) [help]
    ... r/"/><id>/blog/rest-api-graphql-wrapper/</id><updated>2016-05-05T00:00:0 ...

[ghost]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla - and if you have received this in error or have any questions, please drop us a line at cla@fb.com. Thanks!

[ghost]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[leebyron]

Thanks!