Have all intermediate Python notebooks use same data files

Do to changes made after the introductory notebook was created, a
change in filename structure and contents was needed to keep the
lessons simple. This updates the intro lecture to use the same
files as the following lessons.
Rerun intro intermediate Python notebook using new files
Remove old intermediate Python data files
Modifying Mac git install directions

The first line says to download git, but this only works for OSX10.8
and higher. This fix makes clear that this is only for OSC 10.8 and
encourages students to read the second line to find versions for 10.5
- 10.7
Changing wording at Raniere's suggestion
The language "use the most recent available" was confusing to me.
I added "for your OS"
reviewed
added mulit-choice
remove confusing anglification of time machine
changes as suggested by @ctjacobs
fix ../../gloss.html link
in and out burgers, err blocks.
key points and challenge blocks
updated as per #650
Merge pull request #710 from abostroem/fix_git_setup_languages

Modifying Mac git install directions
Merge pull request #719 from danmaclean/creating-lesson-on-regular-expressions

Creating lesson on regular expressions
Reformatting indentation
Merge pull request #497 from ethanwhite/inter-py-filenames

Have all intermediate Python use the same data files
Fixing in/out block error noticed by @r-gaia-cs
Fixing the fix to the in/out block