Improve messaging and instructions around authentication.

Fix for https://github.com/googlegenomics/api-client-r/issues/22
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Added documentation for an additional parameter.

And regenerated all docs per recent changes.
Bug fix for genomic coordinates in vignette.

Incorrectly used coordinates for rs9536314 from the wrong reference.
Incorporated feedback from @siddharthab
Merge pull request #26 from deflaux/master

Fix to improve messaging and instructions around authentication.