v2.1.0

VegaLite v2.1.0

Diff since v2.0.1

Closed issues:

• Separating the specs to a different package (#196)
• Juliacon (#280)

Merged pull requests:

• Julia Package Butler Updates (#281) (@github-actions[bot])
• Remove vega code and rely on Vega.jl (#282) (@davidanthoff)
• Update artifacts (#288) (@davidanthoff)