coverted tutorial to ipynb
reconstituted markdown version of shell tutorial
updated variables.ipynb
Converted tutorial to ipynb
updated data structures notebook
updated flow control notebook
Merge scopatz 'flow-cont' PR 21
Merge scopatz 'vars-types' PR 18
Merge scopatz 'data-struct' PR 20
Merge scopatz 'strings-io' PR 19
added explanation about comparisons, genotype example details
renamed variables, avoiding camelcase
added inline exercise with tests, light-handed change of variable names
Removed math.log example and replaced half-baked examples with more concrete elementary ones.
Expanded examples and converted notebook to v3.
Converted debug tutorial to ipython notebook.
updated debugging tutorial.
Solve issue #44

The 'box' class overflow the window width for some screen size.
This patch fix it using CSS media query.
Fix for issue #44 with large font size

When using large font it will overflow the width so I add
max-width in the css.
Replace Python with Shell

In the box "Text vs. Whatever" it say Python when should say
Shell.

I move this box two paragraphs up to be closer of the lesson
part about writing the file 'middle.sh'.