BUGFIX: includegraphics error in tex -> PDF compilation.

Fix Latex includegraphics error when compiling PDF for Linux Beginner course, by commenting out sed line in Makefile

See merge request !3

Changes post-lsi course, Dec 2015

Don't know why I'm only now getting around to pushing these changes. I think that these are small fixes & improvements based on our teaching the intermediate course in December last year, but the Git Fundamentals course was run since. I hope that they will still merge without much bother...

See merge request !2

add branching

add branching; closing #1

See merge request !1

This reverts commit 5e353cd1.

changed name of Hints section to Tips and Tricks, to be more consistent with the Basics of Scripting section.

added a short mention of operating on string variables in bash sripts to e.g. remove the extension from the end of a filename.