Adding some Highcharts JS themes

[jbkunst]

Hi jrnold,

Time ago I writed a post about a Highcharts theme in ggplot2 and I have a few feedback comments and one of them was about to make a pull request to your package, so here I am.

About the commits I have made:

1. Add R/hc.R file which contains the theme. The template was wsj.R
2. Modify NAMESPACE and DESCRIPTON files. R/ggthemes-data.R to add the backgroud colors and palletes. There are for now 2 themes: defaul, and darkunica.
3. I tried modify vignettes/children/examples.RMD but I can't compile the readme.md (makefile) :(!

Well, that's it. Tell me what you think.

Thanks in advance. Have a nice day.

[jrnold]

Thanks! I merged in the changes.

I made a few changes to theme_hc. I am trying to be consistent in having all theme_* functions have base_size and base_family as their 1st two arguments. Additionally, I thought that bgcolor was a more informative argument name than theme.

[jbkunst]

It's fine, no problem. Thank you too.

[jrnold]

Thanks, again! The new version should be up on CRAN soon.