Merge pull request #11 from raoldroyd/master

Joins, subsetting and aggregation
updates to tutorial
Merge branch 'master' of https://github.com/Robinlovelace/Creating-maps-in-R
minor updates following course
updates to the Rmd: use of sel, removal of fileEncoding and new figure on RStudio
added all updates following November 10th workshop
Merge pull request #1 from Robinlovelace/master

Robins Changes