new badges

[GregorDeCillia]

I really like the idea of this package and would like to contribute a couple of new badges. Are you, @GuangchuangYu, willing to review a PR for the following badges?

• GitHub last commit: example
• GitHub code size example
• CRAN version: example
• CRAN downloads: example
• travis build-status: example
• coveralls coverage status: example
• lifecycle: example

[GuangchuangYu]

of course, PR is welcome.