interactive demos via github

[mpadge]

@mdsumner you can generate an interactive (rgl or whatever) plot via github with the following steps:

1. Copy the contents of tempdir() to a new github repo,
2. Switch on github pages for that repo (to Master branch)
3. Put links in anglr readme

They still won't display in interactive mode on your readme, but at least that will maintain github stuff within github, and with a generally nicer aesthetic than rpubs. Example tempdir() contents from a mapview call are here, with the link going straight to the interactive demo. This workflow also means that you can edit the demos, the impossibility of which via rpubs is frankly an utter killer.

[mdsumner]

oh nice, thanks!

[mdsumner]

Done, finally, thanks muchly!