Move the fonts and hex codes in the Data Visualization section out of images into text

[marteki]

After a presentation of our Design Manual's new data visualization section at OpenVis 2017, we received the following feedback from @micahstubbs, who was one of the attendees:

For the MVP, we tried to put this information up as quickly as possible. But for actual accessibility of the information (both ease of use and available to those with disabilities), we should try to move towards something closer to what our Brand Guidelines > Color section is doing.