Added least square fit and other minor changes to day1/session4.
# use glob syntax.
syntax: glob
*.aux
*.dvi
*.log
*.nav
*.snm
*.toc
*.pdf
*.vrb
*.out
*.sty
*.pyc
*.zip
*~
.project
.pydevproject
app.yaml
build
tests/coverageResults
*,cover
tests/.coverage
*.git
*.egg-info
eggs
parts
.installed.cfg
bin
develop-eggs
.gitignore
.DS_Store
index.yaml