presentation follow-up

[peisenha]

grmpy

• [ ] set vartypes for the simulated dataset, for example, int for D and const
• [x] update documentation to latest

general

• [x] remove tight link to labor lecture 04 ... now independent promotion of work. Please add the new link to the notebook and or slides to https://github.com/HumanCapitalAnalysis/labor_economics/blob/master/README.md
• [x] integrate the promotion notebook into travis
• [x] headline software engineering practices is not followed by content in notebook
• [ ] add discussion / interpreation for LATE

presentation slides

• [ ] fix link to GitHub repository
• [x] update init file layout