doc(README.md): add details on how to use Auto Reload Firefox add-on
fix(juicy-ace-editor): change color theme to improve readability
fix(.travis.yml): ignore evm installation error
fix(.travis.yml): install emacs via evm only once
feat(.travis.yml): test both of emacs-24.3 and emacs-24.4
feat(tutorial1.org): begin introduction to dependent type theory in Lean