Addressing comments from Bioconductor...

A few relatively minor comments:

"Looks good. Just a couple of comments -

1. LazyData: true
   Any particular reason why you're setting this to 'true'? I ask because we've seen this cause problems (long delays) when loading packages with substantial data. My recommendation would be to leave this as 'False'.
2. Both httr and ggplot2 are imported in DESCRIPTION. They should be selectively or fully imported in the NAMESPACE."

from: https://github.com/Bioconductor/Contributions/issues/541

Changing LazyData: false means adding data() functions before each command in examples as mentioned here: http://kbroman.org/pkg_primer/pages/data.html

No good reason not to do this so - DONE. 

Using the Roxygen tags to @import ggplot2 and @import httr at the appropriate times changes the NAMESPACE in the appropriate way. 

Advice here:

• http://r-pkgs.had.co.nz/namespace.html
• https://cran.r-project.org/web/packages/roxygen2/vignettes/namespace.html
• https://stackoverflow.com/questions/8597993/does-roxygen2-automatically-write-namespace-directives-for-imports-packages

Once, I worked out how to do this - DONE. 

So basically all done - testing and version bumping required.