Materials for Python sessions of first day.
Small fixes in the md file for the intro to python lesson.
More work on the python intro notebook.
Finished work on intro to python notebooks.
Merge pull request #6 from jkitzes/gh-pages

Update shell lesson
Merge pull request #7 from arokem/python

Python
Link to JK's lessons from the main page.
Merge pull request #8 from arokem/links-from-index

Link to JK's lessons from the main page.
Fix links to @jkitzes material on front page