Remove :author (Google has discontinued support) about meta-tags

[nunommc]

Also, the documentation has got 2 use cases for author and doesn't seem to be returning what was expected.

1 .set_meta_tags author: "http://yourgplusprofile.com/profile/url"
# <link rel="author" href="http://yourgplusprofile.com/profile/url" />

2. set_meta_tags author: [ "Dmytro Shteflyuk", "John Doe" ]
# <meta name="author" content="Dmytro Shteflyuk"/>
# <meta name="author" content="John Doe"/>

This one is not working the way it was expected. Instead is creating a string with both names, rather than 2 meta-tags

[kpumuk]

Resolved in #101