fivethirtyeight 0.2.0

• Added data sets up through February 28, 2017
• Added first crowd-sourced vignettes
• Added global help file for package: ?fivethirtyeight with complete instructions
• Started adding @examples code in help files to convert to tidy data format so that data plays nice with tidyverse tools.
• Other minor changes:
  • Changed to SVG travis logo
  • Removed explicit loading of data in vignette
  • fivethirtyeight main vignette reads data set list from Google Sheets master document https://goo.gl/OT8iHa