First version of sklearn intro IPython Notebook
Removed lesson number
Added an outline

Also removed a cell
Print number of samples in the dataset
Use StandardScaler instead of scale

For simplicity just scale all of the dataset for
grid search.
see: https://github.com/swcarpentry/bc/pull/443#issuecomment-40677511
Optimize max_features instead of n_estimators

Useless to estimate n_estimators, the more the better!
Use a Pipeline to add feature scaling
Removed feature scaling, expanded acronym RMS

Feature scaling is not necessary for Decision Tree and Random Forests:
https://github.com/swcarpentry/bc/pull/443#issuecomment-41324381
first draft of SSH keys for GitHub lesson
Remove import of Pipeline
added conclusion
Replaced Iris example

Iris example was not clear, replaced with another example.
Added also svg and Google Docs url.

Minor changes:
* explain del rings
* removed download of dataset, just link
Fix rendering of code block

Also add $ to tell input from output
1. Adding `helper` field to header (like `instructor` field).
2. Updating `README.md` to explain what it's for.
3. Updating index page validator to check `helper` field.
Addressing comments by @r-gaia-cs
remove OSX specific pbcopy, remove passphrase material, explain random art image
Adding back the glossary checker
Making placeholders for missing glossary entries
Removing parable about startups and education: snarky, and not really informative
Converting to individual challenge div's in the novice shell lessons