Integrating function from coauthornetwork package.

[cimentadaj]

Hi! Thanks a lot for scholar, it's a very interesting package. Inadvertently, I created the coauthornetwork package which does a very simple thing: extracts your coauthor network and visualizes a network of coauthorship.

Of course the package would be much better if it used the already existing functions from the scholar package. Would you be open to integrating the function from coauthornetwork in scholar? @mkiang suggested the idead here and it made sense to me as this is purely a two-function package which will be probably fit much better using the already existing structure of scholar.

I'd adapt the code to match the style/dependencies of the package, of course.

You can check out the package here.

[GuangchuangYu]

This is a neat feature. PR is welcome!