Major R package cleanup.

* Add package documentation
* Fix function documentation across the package
* Fix .Rbuildignore. It was in the wrong path
* Add data files to the R package: posts, posts_sample
* Add examples for all functions
* Remove unused or deprecated functions
* Remove hard-coded paths, replacing them with funciton parameters
* Lots of minor bug fixes to make all examples run
Remove all unused data.
Add continuous integration.
R package build.

Add experimental travis build.
Add missing map dependencies.
Add license to R package.
Remove top users calculations for now.
Create a single function for generating all images.

Add overall and neighborhood images, including: densities and polar time-of-day plots.
Remove all legacy images. These will be re-generated in future commits.
Remove extra manual file.
Split out web plots. Augment with additional neighborhood plots.
Abstract some of the overall plotting functionality. Add map plots. Standardize plot sizes.
Fix height and width settings.
Adds Google Analytics tracking.
Fix neighborhood ordering. Fix plot sizes.
Fix plot sizes.
Re-create many of the original epxloratory images. Fix links from the HTML.