Simple structure introduced.
Added links for the first session.
Corrected axis placement.
Session 02 added.
Modified <.gitignore> to use projects.
Ignored temp files.
Session 03 added.
Typo.
Added materials from the tutorial.
Exercises for the Session 04.
Added the course notes for the Session 04.
Ignored the data folder.
Typos.
Merge branch 'master' of https://github.com/arbox/R_Course_2014-15