adding before-we-start lesson
adding files from iDigBio lesson
adding Makefile to generate html and skeleton files
remove mentions of GUID in data presentation
rewrite lesson
remove unnecessary pdf file
fix file headers

* remove library(knitr)
* specify where figure files should be stored (i.e. subfolder img/), and use
  prefix `r-lesson-` for files so they can easily be identified.
modifications associated with previous commit
adding home page
adding index to Makefile

* also added old content from previous version of README
* the makefile creates README.md from index.md
use headers from new SWC lesson template
changes to html pages from last commit
fix images and their path
Added paragraph about content of repository
fix missing data + merge 05 and 06

By splitting the lesson, the dataset was missing from several topics.
I removed plotting and put it with lesson 05 to avoid duplication of the code
needed to generate the dataset used in plots.
modifications in topics caused by last commit
Merge pull request #93 from fmichonneau/r-lesson-update

R lesson update