biscale 0.1.0

• Added a NEWS.md file to track changes to the package.
• Develop bivariate mapping functionality (bi_ functions)
• Add example data set (stl_race_income data)
• Implement unit testing with both Travis and Appveyor as well as Code Coverage tracking
• Add .github community files
• Add LICENSE
• Add vignette for getting started (biscale)
• Add pkgdown site functionality