Replaced text_content with content

This resolved the Warning: text_content() deprecated. Use parsed_content(x, as = 'parsed').
Minor code formatting

I'm a insufferable pedant so I made sure everything cleanly followed the style guide. Added spaces on either side of = and between function definition and opening {. Also fixed up assignment operators.
Bumped up minor version for bug fix.

Also added ggplot2 to import list since ggsave is used in plot_to_filename
Updated documentation
Updated NEWS file

Mainly: Removed the warning by updating the httr content call
Fixed up some missing documentation
code cleanup
Removed accidental import
fixed another small issue.
Updated unit test for article tagging

Not sure how it was working before because it failed for me on master.
use yaml format as better summary of list return information
update documentation
enable yaml method
explicitly declare json type so that httr parser doesn't fail