epidata 0.3.0

• Added a NEWS.md file to track changes to the package.
• Added a package user-agent to httr calls
• Changed http: epidata URLS to https:
• Moved DESCRIPTION refs to GitLab
• Fixed CRAN check errors due to new epidata API endpoint
• Added 4 new data sources: “Annual wages by wage group”, “Compensation, wages, and benefits”, “Minimum wage”, “Poverty-level wages”